L1 N 130ARJited States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
REARING Tn MEXICAN BEAN BEETLE INDOORS
Neale F. Howard,
Division of Truck Crop and Garden Insect Investigations
It has been necessary at times to rear larvae of the Mexican bean
beetle (Epilachna varivestis Muls.) during the winter for the propaga-
tion of parasites and also for insecticide testing. The methods out-
lined herein have been used with success.
Both larvae and adults are fed the foliage of cranberry bean. For
feeding the larvae, cranberry bean seed is. sown thickly in sand in 8-
inch flowerpot saucers and grown under fluorescent lights (fig. 1).
Sprouting is hastened by placing the seed between moistened porous
paper. A wick of a thin layer of absorbent cotton is placed under the
sand and run through a hole in the side of the saucer to a narrow tray
of water beneath the bench (1). To drill a hole in each saucer a spe-
cial bit made of brass tubini 1/2 inch in diameter with a piece of
steel inserted in one end to fit the electric drill may be used. An
electric saw is employed to out a slot in each side of the brass tub-
ing so thatwhen an abrasive is used, it will out through ceramics,
cement or glass.
For feeding adults for egg deposition, seed is sown thickly in
8-inch pots of soil, and similarly grown (fig. 2). The bean plants
may be grown in the greenhouse, if space is available. About 20
adults, most of them females, are placed on the plants, under a simple
cylindrical cage made of wire screening to fit over a flowerpot. A
larger number of beetles may be placed in a rectangular cage made of
celluloid and oheeseolothwhich holds two or more pots.
When the eggs have been deposited, the leaves bearing them are
removed and clipped with scissors so that only the portion covered by
the eggs remains, to reduce the growth of mold. These eggs are then
placed on blotting paper moistened with a 5-percent solution of copper
carbonate and set in a petri dish and covered.
When the eggs hatch, and before the young larvae have left the
egg clusters (they remain there for several hours), the group is placed
on a bean plant. The beans sprouted in sand in flowerpot saucers are
used when the first pair of leaves reach their maximum size. Two or
three groups of larvae are placed on each saucer of beans, In order
that the leaves may be consumed before the plants deteriorate.
When a fresh supply of food is needed, the larvae are brushed off
the old plants onto fresh plants with a camel's-hair brush. The old
plants may be out with shears to facilitate the operation. As the
larvae grow, fewer are placed on each saucer of plants. For insec-
ticide tests it has been determined that third-instar larvae are best.
UNIVERSITY OF FLORIDA
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The optimum temperature for the development of the larvae is
about 820 F., and the relative humidity approximately 50 percent. If
sufficient plants are kept in a room, no artificial humidification is
necessary, but at times humidity iust be supplied. Free circulation
of warm air is beneficial, especially when the methods described above
are followed; so an electric fan is kept cDerating much of the time.
The larvae may be placed on potted beans without a cage over them if
cor.itions in the room are suitable. Lima beans may be grown in a
similar manner for rearing the corn earworm (Heliothis armigera (bn.)).
(1) Waters, Harold.
1937. Methods and equipment for laboratory studies of insecti-
cides. Jour. Econ. Ent. 30: 179-203.
growing in flower-
pot saucers under
grown in pots