Title: Florida Entomologist
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00098813/00238
 Material Information
Title: Florida Entomologist
Physical Description: Serial
Creator: Florida Entomological Society
Publisher: Florida Entomological Society
Place of Publication: Winter Haven, Fla.
Publication Date: 1948
Copyright Date: 1917
Subject: Florida Entomological Society
Entomology -- Periodicals
Insects -- Florida
Insects -- Florida -- Periodicals
Insects -- Periodicals
General Note: Eigenfactor: Florida Entomologist: http://www.bioone.org/doi/full/10.1653/024.092.0401
 Record Information
Bibliographic ID: UF00098813
Volume ID: VID00238
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: Open Access

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Florida Entomologist
Official Organ of the Florida Entomological Society

VOL. XXXI MARCH, 1948 No. 1

United States Department of Agriculture, Agricultural Research
Bureau of Entomology and Plant Quarantine'

Since the end of World War II many new and promising in-
secticides have appeared on the commercial markets. Both
State and Federal workers now have under way extensive ex-
periments with these new materials on citrus trees, and a num-
ber of entomologists are employed by insecticide manufactur-
ers to conduct grove experiments. In view of these develop-
ments, it seems appropriate to review an experimental design
for comparing the effects of insecticides under orchard condi-
tions, which consist of a randomized-block arrangement. This
field-plot technique was adopted by the St. Lucie, Fla., labora-
tory of the Bureau of Entomology and Plant Quarantine more
than ten years ago, after it was realized that variations in in-
festation between rows of trees were sometimes sufficient to
invalidate the results of unreplicated row-treatment tests.
Through repeated trials the randomized-block arrangement has
proved to be a practical method for making true comparisons.
Moreover, valid estimates of experimental error can be cal-
culated readily from the data provided by this arrangement.
One of the problems which confront the experimentalist is
natural variation in infestations. With scale insects, for ex-
ample, no two citrus groves have exactly the same amount of
infestation at any one time. Infestations differ in different
localities, and in trees of different varieties, ages, sizes, and
planted at different distances. Individual trees in a single
SK. W. Babcock, L. B. Reed, and especially F. M. Wadley, all members
of this Bureau at the time this work was done, were very helpful in sug-
gesting plot arrangements and methods of analysis.



VOL. XXXI MARCH, 1948 No. 1


President ....-------------.. -- .----------- E. G. KELSHEIMER
Vice President.. .................................. ..... M. C. VAN HORN
Secretary-..-..-..-...-........ ...........-------------.. LEWIS BERNER
Treasurer...-----...... -------------- G. W. DEKLE
Executive Committee............. J. C. GOODWIN
Executive CommJ. T. GRIFFITHS, JR.

H. K. WALLACE ....--.--- ..----.---------..-- Editor
G. B. MERRILL ..............--------- .----Associate Editor
G. W. DEKLE ..-..-- .....----.....-- .....Business Manager

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grove may vary from no infestation to a heavy infestation;
some tree rows may have more scales than others. Border trees
adjacent to an older, heavily infested grove and along dusty
roads usually have heavy infestations.
On the individual tree, scales are usually more numerous in
the top, center, and skirt near the ground, generally as a result
of poor spray coverage. Infestation on the north side may be
quite different from that on the south side of a tree. One
branch may have so many scales that it is killed, and another
may have only a moderate infestation. Even the leaves on a
single branch vary. Old leaves may have few scales, spring-
flush leaves more, and new growth almost none. There is var-
iation even among leaves of the same age and, indeed, in the
number of scales on top surface and lower surface of the same
leaf, or between right and left halves of a leaf.
The season of the year and the weather are important fac-
tors causing variations in infestation. A cold spell which
causes defoliation may reduce infestations to a low level, and
the most exposed trees may show the most effects. Excessive
summer heat may influence the development of scales on one
side of the trees more than on another side. Dashing rains
and winds from one direction may change the pattern of in-
festation. Variations in the distribution of parasites, preda-
tors, and fungi affect the populations of their hosts.
The effect of this universal variability on the results of in-
secticide tests cannot be avoided completely by selecting loca-
tions for tests where the infestations are relatively constant.
However, if a randomized-block arrangement with sufficient
replications of the treatments is utilized and proper sampling
techniques are followed, the effect of the factors that contrib-
ute to natural variation can be minimized.
In setting up a randomized-block experiment for comparing
insecticides for control of scale insects on citrus, we include a
set of unsprayed check trees to demonstrate the natural infes-
tation. A standard insecticide, such as 1-percent emulsible oil,
is also included for comparison with the new insecticides or
For a 10-treatment experiment a block of 120 trees or more
is selected, with few skips, runts, or replants, and with a mod-
erately heavy infestation, as nearly uniform as possible. After
each tree has been examined, a map of the grove is prepared,
and the missing trees, or those showing lack of uniformity, are


indicated by symbols. There must be at least 100 uniform
trees, excluding those in border and ditch-bank rows and those
along dusty roads or on the outside edges of the block. On the
map 10 compact blocks of 10 good trees each are marked off
with circles. These blocks are numbered.
Code letters are assigned to each treatment, usually "0"
for unsprayed, "A" for the standard spray, and "B", "C", "D",
"E", etc., for the new insecticides or treatments to be compared.
Ten corks marked with these code letters are put into a paper
bag, and then drawn out one by one. The trees of block 1 are
marked on the map with the letters as they are drawn. The
corks are put back into the bag and then drawn again for a
similar assignment of treatments to the trees in each of the
other blocks. Thus the assignment of the treatments to the
trees of a block is entirely by chance, and the blocks are ran-
domized. The result is an experiment of ten blocks (replica-
tions), each of which contains one tree of each treatment.
Each treatment is subjected equally to whatever variation in
infestation exists between the different parts of a grove.
The trees are tagged with the code'letter indicated on the
map, to serve as a guide for the application of the different
treatments. It takes longer to spray the scattered trees than
to apply row treatments, but this disadvantage is more than
offset by the elimination of possible effects on data from row
variations or from variation between sections of the grove.
Sampling is done just before spraying, one month and three
months after spraying, and at the end of the year. At shoulder
level around each tree 20 or more leaves are cut off with scis-
sors. New-growth leaves on which infestation has not had
time to develop are not taken. The 20-leaf samples are put in-
to separate 2-pound bags, which are marked with block and tree
designations, and then folded and stuffed into 10-pound sirup
cans. These cans are kept in a refrigerator at 450-500 F. until
the scale counts are made.
For making the counts a binocular microscope is used. The
scales on the leaves are counted and then turned over to see.if
they are living. Records of total and living scales for each tree
and each leaf are tabulated separately. If two men are making
examinations, each examines 10 leaves from each tree; if there
are three workers, each examines 7 from each tree, in which
case the samples must comprise 21 leaves per tree. In this
way the effect of variability between workers is minimized. If


scales are numerous, only half of each leaf may be examined.
The comparisons of the Florida red scale, mature females of
which are present throughout the year, are based on living ma-
ture female scales per leaf, or per half-leaf.
When all samples have been examined, the tree totals, treat-
ment totals, and block totals are calculated. Since the values
so obtained are at best careful estimates, we must analyze the
data statistically before drawing conclusions. Some idea of the
within-treatment (between-tree) variations may be obtained by
calculating the mean number of scales per tree-sample (or per
leaf) and then the standard error for each treatment (Snedecor
1, pp. 41 and 61). If the treatment values differ far beyond
the limits of the standard errors, real differences due to the
insecticide treatments may be assumed.
Much more information can be obtained about our data if
we submit them to an analysis of variance (Snedecor 1, pp. 214-
317). Variance is a numerical measure of variation, and the
error variance for a mean is the square of its standard error.
From the analysis of variance we may estimate the relative im-
portance of the variation between leaves on individual trees
(sampling error) and the variation between trees. The varia-
tion between trees includes the following:
(a) Variation between blocks (replication)
(b) Variation between treatments
(c) Variation due to other factors (experimental error)

The calculation of variance does not require higher mathe-
matics, but merely involves adding the squares of the items
involved, subtracting a correction term easily calculated, and
dividing by the number of items involved less one. Before this
division is made, the different estimates of variation are re-
duced to a common denominator, and the estimate for error is
obtained by subtracting from the total. If the experimental
error is low in comparison with the treatment variance, we may
be reasonably certain that the differences in treatment values
in the table are real and not due to chance variation.
By use of simple formulas (Snedecor 1, pp. 406, 426) it is
possible to calculate the least significant difference and least
highly significant difference between treatment values. If two
treatments differ in living scale populations more than the cal-
culated least highly significant difference, the chances are 99 to
1 that one was actually more effective than the other.


The method of sampling to determine the scale infestation
in the different treatments of extreme importance. As only
fractional samples can be examined, the infestation estimates
based on them differ from the whole, and to the extent to which
they have been subjected to other causes of bias. If small sam-
ples are taken from each of the trees that are treated alike, it
may be expected that the means will reflect the total infestation
more accurately than means of large samples taken from only
one or two trees. Bias can be avoided to a large extent by
taking the samples at random in the manner which has been
From the sampling error and experimental error it is pos-
sible to test the probable effects of increasing the size of the
sample and number of blocks replicationss) on the treatment
values. In our experiments with scale insects many such cal-
culations have indicated that little increase in accuracy (reduc-
tion of standard error) .is to be gained by increasing the num-
ber of leaves per tree from 20 to 50 or even to 100. More gain in
accuracy comes from increasing the number of replications, but
beyond 10 or 12 the diminishing returns in accuracy do not
justify the extra work involved. With 20 leaves per tree and
10 replications, results from recent randomized-block experi-
ments with insecticides against scale insects have been entirely
satisfactory. This arrangement has been used also for insec-
ticide experiments with the citrus rust mite, the citrus red mite,
whiteflies, grasshoppers, the little fire ant, and, indeed, has been
found suitable for experiments with many deciduous fruits and
vegetable crops (Kelsheimer 2).
By adopting the randomized-block arrangement for insecti-
cide experiments on citrus, we have reduced the interference of
variations in infestation between parts of groves and between
rows. We have been able to segregate and compare the magni-
tude of treatment variations, which are our main interest, and
other sources of variation in results. Small differences in re-
sults can be determined as significant and due to the insecti-
cides, or as chance differences due to experimental variation.
Proper sample size and the most adequate number of treatment
replications can be determined for the particular insect under
experiment. The excessively large size of the samples formerly
examined can be reduced without loss in accuracy of results.
From the randomized-block arrangement, with its opportuni-


ties for critical analysis of data, we can draw conclusions with
much more assurance than from former arrangements.

1946. Statistical methods, 4th ed. 485 pp. Ames, Iowa.
1947. DDT treatments for control of mole-crickets in seed-
beds. Fla. Agr. Expt. Sta. Bul. 434.

The annual meeting of the Florida Entomological Society
opened at 1:30 P.M., Friday, December 12, 1947, in room 404,
Newell Hall, University of Florida, with president Max R. Os-
burn presiding.
President Osburn requested each person to rise and give his
name, business connection, and address. It was then announced
that all committees except the auditing committee had been ap-
pointed. Mr. Norman C. Hayslip was named to this committee
with the privilege of selecting someone else to assist him in au-
diting the books of the treasurer-business manager. Following
these preliminaries, the president gave a few words of greetings
to the society and then asked the vice president, Dr. E. G. Kel-
sheimer, to take the chair. Dr. Kelsheimer then presented Mr.
Osburn as the first speaker of the day. Mr. Osburn's paper
was titled "Comparison of DDT, Chlordane and Chlorinated
Camphene for Control of the Little Fire Ant." After the presi-
dential address, the other papers were presented in the order
listed below:
"Mosquito Collecting in the Vicinity of Fort Clinch." J. W.
"Notes on the Collection of Larra americana Sauss., a para-
site of the Puerto Rican Mole Cricket." E. G. Kel-
"Laboratory Substitutions for Certain Types of Preliminary
Field Tests." C. F. Ladeburg.
"Some Results of Recent Work on the Newer Insecticides at
the Orlando Laboratory." W. V. King (presented by
B. V. Travis).
"Border Influences of Serpentine Leaf Miner Infestations
in Potato Fields." D. 0. Wolfenbarger.


"Results of the Use of Concentrated Sprays for Grasshopper
Control." John R. King and J. T. Griffiths.
On Friday evening, the annual dinner was held at the Prim-
rose Grill. The table was decorated in a Christmas motif by
Mrs. Frank N. Young, wife of the chairman of the banquet
committee. The dinner began with a vocal solo by Mr. D. U.
Duncan accompanied on the piano by Mrs. Helen Wallace.
President Osburn then introduced Dean Harold H. Hume, pro-
vost of agriculture at the University of Florida, who gave a
most interesting discussion of the growth, problems, and needs
of the University. Following Dean Hume's talk, the president
introduced the speaker of the evening, Mr. W. G. Bruce of the
U. S. Department of Agriculture, who addressed the society on
the subject of the "Progress of Entomology." Fifty-eight mem-
bers and guests attended the dinner.
On Saturday morning, December 13, at 8:30 A.M., the meet-
ing of the society reconvened and was called to order by the
president. The following papers were presented:
"Results of over 100 inches of Rains on the Mosquito Popu-
lation of Palm Beach County." Ed. Seabrook.
"Phyllophaga elizoria, a Maybeetle, Damaging Young Orange
Trees (Coleoptera, Melolonthininae)." W. H. Thames.
"Randomized Block Arrangement for Insecticide Experi-
ments on Citrus Trees." Herbert Spencer and Max R.

Following the presentation of papers, a business meeting of
the society was called. The report of the secretary was ap-
proved without reading since it had been published previously in
the Florida Entomologist. There was no old business. The
president then called for new business. The secretary read a
letter from the president of the Sociedad Entomologica Argen-
tina requesting that the Florida Entomological Society exchange
publications with it. This was approved by the members. The
secretary presented the problem of exchanges of publications
with other societies. It was then moved, seconded, and passed
that the secretary be empowered to establish exchanges with
other organizations. The possibility of securing subsidation for
the publication of the Florida Entomologist from the University
of Florida library was then suggested. It was moved and sec-
onded, and then passed by the society, that subsidation would be


acceptable to the organization. It was also moved and sec-
onded and passed that the exchange library of the Florida
Entomological Society be permanently housed in the University
-of Florida library, if it could be so arranged with the the Uni-
versity librarian.
The president then announced that the present treasurer-
business manager, Mr. J. C. Crevasse, Jr., had submitted his
resignation and that it was accepted by the executive committee.
Mr. W. G. Bruce thanked the society on behalf of the Texas
Entomological Society for its expression of good wishes for the
success of the Texas Society's annual meeting, and then re-
turned the greetings to the Florida Society.
Dr. A. N. Tissot read a letter addressed to the late Professor
J. R. Watson from an entomologist in Germany. The letter
described the plight of the scientists in Europe and requested
that, if possible, the society send some sort of aid. It was sug-
gested that each person present might contribute fifty cents,
the total sum collected to be used in sending food to the writer
of the letter. A total of $20.50 was obtained and turned over
to Dr. Tissot for purchase of food and cost of mailing.
Dr. J. T. Griffiths raised the question of the site for the
next annual meeting of the Society and suggested that it not be
held in Gainesville. Dr. Travis extended an invitation for the
meeting to be held in Orlando, during which time the members
of the organization would have an opportunity to inspect the
U. S. D. A. laboratory there and see the methods of research
being used in the study of insecticides. It was moved and sec-
onded that the next annual meeting be held in Orlando. The
society approved unanimously. There was some discussion
about the date of the meeting; however, it was decided to let
the executive committee decide the matter.
The report of the membership committee was then called
for by the president. In the absence of the chairman of the
committee, Dr. Frank N. Young presented the names of the per-
sons listed below for the following classes of membership:
Associate members to be active members:
R. E. Bellamy J. S. Haeger
J. M. Bellows E. R. Jones, Jr.
I. J. Cantrall R. B. Kleinhans
C. M. Crutchfield Douglas Maughn
C. J. Goin W. H. Merrill
W. B. Gresham, Jr. R. C. Morris
J. T. Griffiths Thomas Smyth
A. B. Grobman


Associate membership:
P. S. Arey J. R. King
Mrs. Ernestine Basham F. P. Lawrence
W. J. Decker J. D. Rebstock
Fred Dexheimer Ed. Seabrook
J. J. Diem C. C. Skipper
Kelvin Dorward D. J. Taylor
P. E. Frierson H. T. Vanderford
L. A. Hetrick R. K. Voorhees
D. W. Hookom R. T. Wallace
S. B. Hopkins, Jr. M. J. Westfall
,Student membership:
C. E. Bingaman W. W. Neel
Herndon Dowling G. R. Reid
S. K. Eshleman R. V. Roig
R. W. Hudson D. R. Sapp
E. W. Knetch E. L. Solomon
E. R. Krestensen M. L. Wright, Jr.
Dr. J. W. Wilson moved that the report of the membership
committee be accepted and that the persons named be accepted
as recommended. The motion was seconded and passed unani-
Because of the absence of the treasurer-business manager,
a financial report was not given.
The president then called for a report of the nominating
committee. The chairman, Dr. A. N. Tissot, presented the fol-
lowing candidates:
President-E. G. Kelsheimer
Vice President-M. C. Van Horn
Secretary-Lewis Berner
Treasurer-business manager-G. W. Dekle (for two years to
fill out the unexpired term of J. C. Crevasse, resigned)
Editor of the Florida Entomologist-H. K. Wallace
Associate editor-G. B. Merrill
Member of Executive Committee-J. T. Griffiths (two year
It was moved and seconded that nominations be closed.
Mr. W. G. Bruce requested that the secretary be instructed to
cast a unanimous ballot for the election of the above named
candidates. This was passed by the society.
Mr. Max Osburn, retiring president of the society, then
turned the chair over to the incoming president, Dr. E. G.
Mr. Hayslip, who earlier in the meeting had been appointed
to the auditing committee, requested that a Gainesville member


be substituted in his place to audit the books of the resigning
treasurer-business manager. Dr. Kelsheimer then appointed
Dr. A. N. Tissot to this committee.
The annual meeting was adjourned at 10:15 A.M.
A total of fifty-three persons signed the attendance registry.
Respectfully submitted,

United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
The presence of the little fire ant (Wasmannia auropunctata
[Roger]) in the United States, was first noted by Smith (1929)
in 1929, in Florida. Later in the same year Wheeler (1929) re-
ported that he had received specimens of this ant from Florida
in 1924. Several years later Keifer (1937) reported that the
little fire ant was established in Los Angeles County, California.
Since its discovery in southern Florida, the little fire ant has
spread northward into nearly all sections of the peninsula. At
the present time it is a serious household pest in many areas,
and an important pest to citrus-grove workers in some sections
along the east coast of Florida (Spencer 1941, Osburn 1945).
Recently Wolfenbarger (1947) reported that it caused disturb-
ance among fruit pickers in a large guava grove near Opa Locka,
Fla. According to Wheeler (1929) it is probably that the little
fire ant may eventually become established in green houses in
many parts of the United States, but will be able to survive out-
of-doors only in the tropical portions of the country.
The worker ants visit the citrus trees to obtain honeydew
secreted by aphids, mealybugs, whiteflies, and other insects.
In heavily infested groves millions may be present. At times
the trunks of citrus trees take on a reddish-brown cast, owing
to the presence of so many individuals moving up and down the
trees. The worker ants are small, and ordinarily not aggres-
sive. They usually sting only when they are pressed or con-
fined between the clothing and the skin. When trapped under
these conditions-it is practically impossible to work in a heavily


infested tree without getting them under the clothing -they
sting viciously by humping the thorax, lowering the posterior
part of the abdomen, moving forward, scratching the skin, and
depositing poison all in one operation. Some time may elapse be-
tween the actual sting and the realization by the victim that he
is literally on fire. Often, the ant has disappeared in the mean-
time, and the opportunity to crush the tormentor has passed.
Citrus-grove workers, especially fruit pickers, have refused at
times to work in trees infested with this ant, and in other in-
stances have left trees partially picked or demanded premium
In citrus groves the ant nests in the soil or under fallen
branches, leaves, fruit, or almost any type of debris found on
the ground. The nests have no definite form, and consist of
clusters of ants that vary considerably in numbers. In some of
these nests workers, one or more queens (with or without
wings), and eggs, larvae, and pupae have been found. In others
only workers seem to be present, although the other forms may
be farther down in the soil. The nests seem to be temporarily
located, and during periods of extreme dryness the ants go deep-
er into the ground. Under extremely wet weather and flood
conditions entire colonies may be found up in the limb crotches
of trees or under pieces of loose bark.
DDT sprays and dusts have been very effective in killing the
little fire ant and preventing troublesome reinfestations for
periods of two months or longer, depending upon the concentra-
tion and quantity of material used (Osburn and Stahler 1946).
One cooperative growers' association in St. Lucie County, Fla.,
treated over 400 acres of citrus during the past season in order
that its grove hands could work without discomfort.
Since DDT first appeared as an insecticide, other chemicals
have been developed which are showing insecticidal properties.
Two of these, chlordane and chlorinated camphene, became
available for experimental work during 1947. After prelimin-
ary tests indicated that they were effective against the little
fire ant, critical field tests were made to compare their residual
The tests were carried on in St. Lucie County in an old
grapefruit and orange grove that was heavily infested with the
little fire ant. The sprays were prepared by dissolving 8 ounces
of either technical DDT, technical chlordane, or technical chlori-


nated camphene in one-half gallon of Number 2 fuel oil, adding
19 ml. of phthalic glyceryl alkyd resin to make a stock emulsion,
and then diluting the emulsion with water to make 100 gallons.
The concentration of 8 ounces per 100 gallons was chosen be-
cause this amount of DDT has provided the best control with a
minimum of cost. Generally, lesser quantities of DDT are not
so effective, and little is gained by using greater amounts. Even
though previous work had shown that oil sprays used alone at a
concentration as high as 1.6 per cent were ineffective in con-
trolling the little fire ant, a spray containing 1/2 gallon of fuel
oil per 100 gallons of water was included in the experimental set-
up as a check. The sprays were applied thoroughly with a pow-
er outfit to the tree trunks and larger lower branches. Ap-
proximately 4 gallons of spray was used per tree.
The experimental design was that of randomized blocks.
There were five replications of each treatment, and a single tree
in each block received each treatment. Before the treatments
were applied, a band 1 inch wide was stenciled with white paint
around each tree trunk, below the lowest branch at from 2 to 3
feet above the ground level. The circumference of the tree
trunks at this point ranged from 29 to 38 inches. At intervals
following the applications, the treatments were compared by
recording the number of ants on five of these bands per treat-
ment, or a total area of slightly more than 1 square foot of tree-
trunk surface per treatment. The data were analyzed statis-
A summary of the results is presented in Table 1.

(8 oz. of specified material in z
gal. No. 2 fuel oil per 100 gal. of July July Aug. Aug. Sept. Sept. Oct.
water) 10 24 7 22 5 26 27

DDT ..............................-............. 1 0 17 126 20 21 3
Chlordane ..............-- .......................... 1 0 29 65 25 7 13
Chlorinated camphene .................... 1 3 6 60 42 51 11
Fuel oil alone (check) .................... 225 294 658 793 884 411 99
Difference required for
significance at 5% level ............ 50 60 171 119 112 262 44

SFuel oil in all treatments made emulsifiable by adding 19 ml. of phthalic glyceryl
alkyd resin to the oil.


The data,, taken at approximately biweekly intervals from
the time of application through September 26, and again on
October 27, 1947, showed that DDT, chlordane, and chlorinated
camphene were equally effective against the little fire ant, and
that the fuel oil used alone was of no value. At no time was
there a significant difference in effectiveness between the three
insecticides; on each examination date all of them were signifi-
cantly better than the oil alone.
The three treatments reduced and held the infestation to a
low level until August 22, when their effects seemed to be dis-
appearing, as more ants were found than on previous dates.
Apparently the increases were due to ants that had developed
after the materials were applied, and had not been exposed to
the spray residues long enough to be affected. In confirmation
of this theory, large numbers of dead ants that had not been
there on August 22 were found at the bases of treated trees at
the time of the next examination. On September 5, fewer ants
were recorded in the three effective treatments, whereas the in-
festation increased in the oil treatment. These reductions were
probably due to the residual qualities of the materials.
In the treatment consisting of fuel oil alone the ant infesta-
tion increased steadily until September 5. Shortly thereafter,
during the week of September 14, a hurricane accompanied by
heavy rains caused a reduction in ant activity, so that on Sep-
tember 26 only about half as many ants were present on the
check trees as were found on September 5. Continued heavy
rains and flooded grove conditions throughout the last of Sep-
tember, and most of October, were responsible for a further re-
duction in ant activity, as reflected in the records made on
October 27.
The results of the work indicate that both chlordane and
chlorinated camphene compare favorably with DDT for control
of the little fire ant.
Sprays containing equal quantities of DDT, chlordane, or
chlorinated camphene in No. 2 fuel oil were compared for the
control of the little fire ant (Wasmannia auropunctata. [Roger])
on citrus trees. At the rate of 8 ounces per 100 gallons of
water, the three materials were found to be equally effective
and to reduce infestations significantly for a period of at least
12 weeks, when sprayed on trunks and larger limbs. No. 2 fuel
oil used alone at a strength of 0.5 percent was of no value.


1937. Systematic entomology. Calif. Dept. Agr. Bul. 26 (4): 435.
1945. DDT to control the little fire ant. Jour. Econ. Ent. 38 (2):
1946. Use of DDT to control the little fire ant. U. S. Bur. Ent. and
Plant Quar. E-683, 3 pp.
1929. Two introduced ants not previously known to occur in the
United States. Jour. Econ. Ent. 22 (1): 241-243.
1941. The small fire ant Wasmannia in citrus groves. A preliminary
report. Fla. Ent. 24 (1): 6-14.
1929. Two neotropical ants established in the United States. Psyche
36 (2) : 89-90.
1947. Tests of some newer insecticides for control of subtropical fruit
and truck crop pests. Fla. Ent. 29 (4): 29-44.

Sub-Tropical Experiment Station

The manner in which insects infest plants and distribute
themselves in a field is of interest and may be of value in deter-
mining control measures. Insects may be in a field prior to
seedbed preparation and planting and infest plants as they be-
gin growth. They may infest plants in the seedbed and be dis-
persed by man during transplanting. They may enter a field
from the outside during the growth of the crop and become dis-
persed evenly over a field. They may, on the contrary, be un-
equally distributed because more insects stopped along the field
border near the point of entry. Equalization of population or
small and insignificant differences in distributions of a species
over fields are attributable to two factors operating singly or in
combination. These are (1) dispersability of an insect species,
and (2) small fields or short distances under observation.
These factors are considered to be operating where it appears
that insects are evenly dispersed.
Interest is directed in this presentation to unequal distribu-
tion of insects, particularly to those cases in which more in-
sects were observed nearest the insect sources outside of a
field. It is recognized that unequal distribution of insects over
a field, or border effects, may result from (1) unequal disper-


sion from an outside source, (2) a converging or massing of in-
dividuals of a species in areas with more favorable local condi-
tions, or (3) other factors. In this presentation the border ef-
fects of the serpentine leaf miner, Liriomyza pusilla (Meig.), in
potato fields are attributed to unequal dispersion from outside
Larvae of the serpentine leaf miner, restricted as they are to
feeding between leaf surfaces, disperse very short distances, in
terms of inches, from the point of egg deposition. Pupae of the
leaf miner may be distributed by dispersion agents such as man,
wind, water, or by other agents. The distance might be con-
siderable but is usually negligible. The adult fly is the active
disperser of the species. It was reported by Webster and Parks
(1913) that the adult serpentine leaf miners emerging from hi-
bernation "do not travel far before oviposition takes place."
Information on definitive distances to which the serpentine leaf
miner disperses are as woefully lacking as are those of most
other insect species.
Marginal influences of fly activities were reported by Wolf-
enbarger (1947) for the severe leaf miner infestations recently
encountered. As they became more abundant border effects
were distinctly observed in several fields of tomatoes and po-
tatoes, in large commercial fields. The tomato plants, first
started in the fields in the area, attained large size and were
heavily infested before the potatoes were attacked, so the toma-
to plants might have appeared to be a primary host plant of the
Near the time of tomato maturity, the potato plants had
grown so that they were attractive to the leaf miner adults.
Definite fly dispersions were observed at this time. There were
gradual and continuous movements of flies occupying days or
even weeks of time. Flies were collected in nets, they were ob-
served on the leaves, and a few days later plant symptoms of in-
festations were in evidence. These observations demonstrated
that more flies were present where potatoes were planted to the
west of tomatoes. Dispersion effects were less evident in po-
tato fields to the south and to the north, and least to the east of
tomato fields, showing decidedly directional effects.
Insects are generally considered to have their dispersion ac-
tivities altered but little by winds. During the preparation of a,
summary on the dispersion of small organisms, Wolfenbarger
(1946), references were encountered in which authors reported


or alluded to winds which actively dispersed insects. Part of
these references were devoid of numerical evidence. Most ref-
erences which gave data showed little or no directional in-
fluence of insect dispersion attributable to winds. Insects, in
general, are believed to seek shelter from winds which blow
them about; they tend to control their dispersion activities. It
is expected, however, that exceptions to this generality must
During the observations on the dense leaf miner infestations
the prevailing winds, although gentle, were from easterly direc-
tions. They were damp winds from the ocean but had passed
over some 3 to 6 miles of land. It seems likely that the winds
may have been instrumental in aiding dispersions toward the
west. It might be questioned, however, whether the wind was
an agent of propulsion toward the west or whether there was a
repulsion affecting the easterly direction of fly dispersion.
LEAF MINES: In one large 80-acre field of potatoes, bordered
on the east end by tomatoes, leaf miner infestation evidence was
very marked. Counts of leaf mines per potato leaf were made
at different distances from ,the end of the field. The average
number of leaf mines decreased with distance increase from the
margin of the potato field, as shown by the data in Table 1.

Distances classes, feet 0-40 41-80 81-120 121-160 161-200 201-240 241-280
Avg. No. of mines
per leaf 76 67 64 56 31 30 17
A regression curve was drawn from these data, according to
the regular method of least squares, except that distances were
transformed to logarithms as discussed by Wadley and Wolfen-
barger (1944). The curve is expressed by the formula:
Expected number of leaf mines = 152.3708 50.6919 (log of distance).
The curve is illustrated in Fig. 1. The coefficient was found
to be highly significant. At distances greater than about 300
feet the border effects were reduced to low levels. Beyond this
distance infestations appeared to be more or less uniform in the
remainder of the field.
The rates of border effects observed in other fields ap-
peared similar to the one illustrated above. More marked dif-
ferences were observed in fields during the earlier stages of in-




200 400


Figure i.-Serpentine leaf miner injuries and potato yields as related to
field border.

festation than in the later ones. These differences were due to
primary invasions since insufficient time had passed for the
flies to have developed on potatoes. In later stages of infesta-
tions a greater equalization of leaf mines over the fields was
evident. The equalization of units at later times or in later
stages of infestation was a factor discussed by the author, Wolf-
enbarger (1946), in a summary on dispersion, under the sub-
head of, "Dispersion Equalization in Time Sequences." This
factor is undoubtedly a matter of slight importance in some
cases and of considerable importance in others.




A Ft. from margin 18 200 300 350 400 450 500 550 600
Yield, bu. per A. 129 136 143 165 163 177 155 163 184
B Ft. from margin 9 34 56 78 119 150 193 228 268 303 349
Yield, bu. per A. 239 193 209 238 184 268 295 270 232 314 259
C Ft. from margin 25 127 229 331 433 535
Yield, bu. perA. 134 154 141 113 132 157


YIELD RESULT: Sections of potato rows were measured, dug,
and the yield data were converted to bushels per acre, as taken
from each of three potato fields at different distances from the
eastern edges. These data are summarized in Table 2.
Border effects of leaf miner dispersions were observed re-
peatedly in each of these fields. Two curves were drawn for
these yield data. The field designated "A" in Table 2 was the
field in which the data on leaf mines (Table 1) were collected.
A curve was drawn to smooth these data, Fig. 1, "Field A."
Another curve was drawn from the combination of data from
the three fields, Fig. 1, "Fields combined." These indicate the
magnitude of yield increases with distant increases. The gen-
eralized regression formula obtained from the data in Table 2
Expected yield = 131.2942 + 28.5678 (log of distance).
The results of computations from the use of the formula for
selected distances showing the theoretical or expected yield at
each are given as follows:
Distance, ft. from field border 9 100 300 400 600
Yield, bu. per acre 171 188 202 206 211

A comparison of the curves illustrating yields, Fig. 1, shows
similar curvilinearities, indicating how the data from the one
field tended to agree with those of the combined fields.
In a consideration of the curves, Fig. 1, the leaf mines' curve
bends more sharply than those of the yields. This is attributed
to the equalization of fly population, as discussed above. The
data on leaf mines per leaf were taken at a time when the border
effects were more marked. The yield data on the other hand,
include effects of accumulated attacks of the miner over the
growth period of the plants.
SUMMARY- Dense populations of the serpentine leaf miner
developed in tomato fields and dispersed in westerly directions
into adjoining potato fields. Data taken on the rate of decrease
as related to distance increase from the field border showed that
at about 300 feet leaf mines reached low levels that were gen-
eral for the entire fields. Potato yields in three fields were
found to increase with distance increase from the border where,
based on the regression formula, 171 bushels per acre at 9 feet
from the border increased to 202 bushels per acre at 300 feet.


WADLEY, F. M. and D. O. WOLFENBARGER. Regression of insect density on
distance from centers of dispersion as shown by a study of the smaller
European elm bark beetle. Jour. Agr. Res. 69: 299-308, illus. 1944.
WEBSTER, F. M. and T. H. PARKS. The serpentine leaf miner. Jour. Agr.
Res. 1: 59-87, illus. 1913.
WOLFENBARGER, D. O. Dispersion of small organisms, distance dispersion
rates of bacteria, spores, seeds, pollen, and insects; incidence rates of
diseases and injuries. Amer. Midi. Naturalist 35: 1-152, illus. 1946.
...-----.-........ -----............ The serpentine leaf miner and its control.
Fla. Agr. Exp. Sta. Press Bul. 639. 1947.

Cyrtopeltis varians (Dist)
By J. W. WILSON, Entomologist
Florida Agricultural Experiment Station

During the course of investigations, at the North Florida
Experiment Sation, Quincy, Florida in July, August and Sep-
tember, 1947, of means of controlling the green peach aphid,
Myzus persicae (Sulz.), a small brown mirid was observed in
large numbers on numerous occasions feeding on this aphid.
During September, in a two acre field of shade tobacco that had
been harvested and allowed to produce suckers, this mirid be-
came so abundant that the previously heavy infestation of
Myzus persicae was practically destroyed. In a tobacco seed
bed planted for experimental purposes the mirids reduced the
aphid population to such a point that investigation of chemicals
for apid control could not be continued. Specimens were sent
to Dr. C. F. W. Muesebeck, Division of Insect Identification,
Bureau of Entomology and Plant Quarantine, for identification.
These specimens were identified by Dr. R. I. Sailer as Cyrtopel-
tis varians (Dist.). In his letter, Dr. Muesebeck stated that
this insect had been reported as a predator on the suckfly
Dicyphus minimus Uhl. and as injurious to tomatoes. From
these reports it seems that C. varians may be both predacious
and phytophagous. On one occasion during August several
specimens (6 to 10) of C. varians were observed in the field
feeding on about a third instar larva of Protoparce sexta (Jo-
han.). Since this insect was observed only once in the act of
feeding on a small tobacco hornworm larva it is not known that
it will attack larger hornworm larvae.


Department of Biology and Geology
University of Florida

Stoneflies are not a conspicuous element in the insect fauna
of Florida. Because of the paucity of species over most of the
state, only five forms have thus far been recorded in the litera-
ture. These are Pteronarcys dorsata (Say) listed by Claassen
in 1931,1 and Taeniopterayx maura (Pictet), Leuctra decepta
Claassen, Acroneuria xanthenes (Newman), Acroneuria lycor-
ias (Newman) recorded by Frison in 1942.2
During the years 1937-1940, several lots of stoneflies were
collected by the writer while gathering material on mayflies.
These specimens were sent to the late Dr. T. H. Frison, chief of
the Illinois Natural History Survey, for identification. It ap-
peared advisable to the author to publish the list of Dr. Frison's
identifications so that there might be established a basis for
future Plectoptera work in Florida.
Occasional specimens from southern Alabama and from
Georgia were also taken. Records of those specimens, also
identified by Dr. Frison, are included in this paper.
The classification followed below is that established by Fris-
on in his most recent work on the Plecoptera.2

Family Pteronarcidae
Pteronarcys sp.
Florida: Liberty Co., River Junction. March 17, 1939.
Family Taeniopterygidae
Taeniopteryx nivalis (Fitch)
Florida: Holmes Co., Sandy Creek. December 11, 1937 and December
14, 1939. Liberty Co., Sweetwater Creek, Torreya State Park.
December 1, 1939. Washington Co., Holmes Creek. December 11,
1937 and December 14, 1939.
Georgia: Burke Co., Briar Creek. September 5, 1938. Coll. H. H.

Claassen, Peter W. 1931. Plecoptera Nymphs of America (North of
Mexico.) Charles C. Thomas, Publisher, Springfield, Illinois.
2 Frison, T. H. 1942. Studies of North American Plecoptera with
special reference to the fauna of Illinois. Bull. Ill. Nat. Hist. Sur. Vol.
22, Art. 2.


Family Nemouridae
Nemoura venosa Banks
Florida: Leon Co., Tallahassee. March 18, 1939. Liberty Co., Torreya
State Park. May 7, 1933.

Family Leuctridae
Leuctra decepta Claassen
Florida: Leon Co., 12 miles west of Tallahassee. November 30, 1939.
Leuctra triloba Claasseen
Florida: Leon Co., 12 miles west of Tallahassee. November 30, 1939.
Leuctra sp.
Georgia: Lumpkin Co., Walnut Creek. April 29, 1938.

Family Perlidae
Atoperla ephyre (Newman)
Florida: Holmes Co., Sandy Creek. December 11, 1937. Liberty Co.,
Torreya State Park. December 10, 1937.
Alabama: Escambia Co., Perdido Creek at U. S. Hwy. 31. June 3,

Neoperla clymene (Newman)
Florida: Alachua Co., Hogtown Creek, Gainesville. February 19, 1934.
Gainesville. January 8, 1938, January 16, 1938, and February 3,
1938. Worthington Springs. February 5, 1939. Bay Co., 26 miles
north of Panama City at Fla. Hwy. no. 77. June 8, 1938. Hamil-
ton Co., Jasper. February 4, 1938. Hillsboro Co., Six-Mile Creek,
near Tampa. March 26, 1938. Bell Creek. March 26, 1938. Oka-
loosa Co., Niceville. June 7, 1938. 9.1 miles west of Walton Co.
line at Fla. Hwy. no. 20. May 31, 1940.
Georgia: Dougherty Co., Lake Worth, Albany. June 26, 1940. Coll.
H. H. Hobbs.

Perlesta placida (Hagen)
Florida: Alachua Co., Hatchet Creek. October 11, 1939. Bay Co., 26
miles north of Panama City at Fla. Hwy. no. 77. June 8, 1938.
Gadsden Co., River Junction. March 17, 1939. 5 miles south of
River Junction. June 6, 1940. Hamilton Co., Jasper. February 4,
1938. Jackson Co., Blue Springs Creek, Marianna. May 5, 1939
and June 5, 1940. Leon Co., Tallahassee. March 16, 1939 and June
5, 1938. Liberty Co., Little Sweetwater Creek. June 10, 1938.
Sweetwater Creek, Torreya State Park. June 10, 1938. Okaloosa
Co., Crestview. December 12, 1937. 5.1 miles west of Walton Co.
line at Fla. Hwy. no. 20. May 31, 1940. Walton Co., 5.4 miles west
of Washington County line at Fla. Hwy. no. 20. May 31, 1940. 9.5
miles west of Portland. May 31, 1940. Portland. April 13, 1938.
Freeport. April 2, 1939. Washington Co., Holmes Creek. April
2, 1938.
Georgia: Jones Co., 10 miles north of Macon. April 30, 1938. Rabun
Co., Small creek flowing into Lake Burton. June 22, 1940. Coll.
H. H. Hobbs.

VOL. XXXI-No. 1 23

Alabama: Baldwin Co., Dyas Creek, Dyas. June 3, 1940. Elmore
Co., 4 miles east of intersection of Hwys. no. 14 and 45, Mortar
Creek. June 5, 1940. Mobile Co., 3.5 miles south of Irvington.
June 2, 1940.

Acroneuria lycorias (Newman)
Florida: Liberty Co., Little Sweetwater Creek. June 10, 1938.

Acroneuria arenosa (Pictet)
Florida: Jackson Co., Blue Springs Creek, Marianna. June 5, 1940.

Acroneuria ruralis (Hagen)
Florida: Jackson Co., Blue Springs Creek, Marianna. June 5, 1940.
Georgia: Dougherty Co., Lake Worth, Albany. June 26, 1940. Coll.
H. H. Hobbs.

Acroneuria xanthenes (Newman)
Florida: Liberty Co., Torreya State Park. December 10, 1937.
Georgia: Jones Co., 10 miles north of Macon. April 30, 1938.

Acroneuria abnormis (Newman)
Florida: Wakulla Co., Smith Creek. June 5, 1938. Leon Co., Small
stream flowing into the Ochlocknee River. June 5, 1938.
Georgia: Lumpkin Co., Walnut Creek. April 29, 1938.

Acroneuria sp. B (as designated by Dr. Frison)
Florida: Gadsden Co., River Junction. June 30, 1939. Leon Co.,
Tallahassee. March 17, 1939. Liberty Co., Sweetwater Creek.
December 10, 1937 and July 1, 1939. Okaloosa Co., Niceville. June
7, 1938. Walton Co., Freeport. April 2, 1939.
Georgia: Brian Co., Canoochee River. December 18, 1939. Coll. H.
H. Hobbs. Screven Co., Beaver Dam Creek. September 7, 1938.
Coll. H. H. Hobbs.

Neophasganophora capitata (Pictet)
Florida: Gadsden Co., River Junction. March 17, 1939.
Togoperia immarginata (Say)
Alabama: Mobile Co., 1.4 miles south of Kushla, Seabury Creek. June
3, 1940.

Togoperla kansensis (Banks)
Florida: Bay Co., 26 miles north of Panama City. June 8, 1938.
Jackson Co., Blue Springs Creek, Marianna. June 5, 1940. Oka-
loosa Co., Crestview. December 12, 1937. Niceville, June 7, 1938.
Shoal River, December 11, 1937. Walton Co., Freeport. April 2,
1939. Ebro. June 7, 1938.
Georgia: Baker Co., Newton. October 29, 1938. Coll. F. N. Young.

Family Isoperlidae
Isoperla confusa Frison
Florida: Alachua Co., Worthington Springs. February 5, 1939.


Raleigh, North Carolina

The description of this genus and species is based on ma-
terial which was submitted to the writer by Dr. A. N. Tissot of
Florida Agricultural Experiment Sation. Material was subse-
quently sent to Doctors E. O. Essig, G. F. Knowlton, and Profes-
sors M. A. Palmer and J. O. Pepper. The writer wishes to
express his appreciation to the above named lady and gentle-
men for their opinions concerning this genus and species.
Xenopterygus new genus
This genus seems most closely related to the Tribe, Fordini;
however, many of the characters resemble those of the Tribe,
CHARACTERS: Cornicles absent. Wax plates present but
poorly developed on head, well developed on thorax (see Fig. 1)
and on abdomen. Alate vivipara with six-segmented antennae,
sensoria broadly transverse to oval; secondary sensoria fringed.
Fore wings with the media simple, hind wings with both media
and cubitus present.
TYPE SPECIES: Xenopterygus ipomoiae

Xenopterygus ipomoiae n. sp.
The distinguishing characteristics of this species are the
fringed secondary sensoria which are often coalesced; chitinous
islands in the primary sensorium on antennal V; and the irregu-
lar enlargements along the cubitus and first anal of the fore
wing and along the cubitus of the hind wing.
ALATE VIVIPARA: Color of living specimens not known.
Cleared specimens show the following characteristic coloration:
dark brown to fuscous on antennae, head, thorax, legs, and
transverse bars on the dorsum of the abdominal segments, espe-
cially segments of IV, V, and VI. Some of the general speci-
mens do not show the conspicuous dark bars on the abdomen
and the appendages are lighter in color.
MEASUREMENTS: Body 1.8 to 2.2; width through eyes .38 to
.43; antennal III, .23 to .27; IV, .07 to .09; V, .10 to .12; VI, .08
1 Research Contribution No. 1 published with the aid of the State Col-
lege Research Fund, Department of Zoology, North Carolina State College
of Agriculture and Engineering of the University of North Carolina.


to .10 plus .02 to .04; rostrum reaching between 2nd and 3rd
coxae; rostral IV, plus V, .09 to .10; hind tibiae .72 to .93; hind
tarsi .15 to .18; cornicles absent.
Antennal III with 7 to 15 sensoria, some of the sensoria are
usually coalesced especially toward the distal end of the seg-
ment; antennal IV, with 1 to 2 sensoria; antennal V without
secondary sensoria, primary sensorium with one or two chitin-
ous islands bearing 1 to 2 hairs (see Fig. 1) ; antennal VI with-
out secondary sensoria, primary sensorium with or without
chitinous island bearing hair. Primary and secondary sensoria
fringed. Fore wings with media simple, cubitus and 1st anal
with irregular enlargements especially near the basal area.
Hind wings with both media and cubitus, cubitus with enlarged
areas. Hairs on hind tibiae short and spine-like, less than one-
half diameter of segment bearing them.

00 r



H. tib.

Figure 1.-Xenopterygus ipomoiae Smith.


TYPES: Holotype and paracotypes in the U. S. National Mu-
seum; Paracotypes and/or paratypes in the collections of Dr.
A. N. Tissot and the writer.
TYPE LOCALITY: Clewiston, Florida.
COLLECTIONS: Clewiston, Florida, on roots of sweet potato
(Ipomoia baa.tats [L.] Lam.) June 1, 1945, holotype slide (3
specimens) and 11 Paracotype slides (22 specimens); during
June, 1944, 30 paratype slides, all collections by W. D. Wylie.
One specimen was located in the U.S.N.M. labeled "on Dash-
een leaf, Guaynabo, Puerto Rico, Flaxon Anderson Mills, Coll.
Dec. 19, 1932, San Juan 3355." This specimen had the anten-
nae missing but the other characters seemed to be the same as
the material from Florida.

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