MEXICAN BEAN BEETLE IN THE SOUTHEAST. 9 
TaBLE 2.—Eggs laid by 69 females of the Mexican bean beetle for which records 
are complete, 1921 and 1922. 
1921 1922 
Generation. Average Average 
Number number N er er! number 
ofeggs per ofeggs per 
females. forinlee females. fornale: 
Ovenwintered penerabionss-se-as asses ae see ieee ee = | 10 507 15 252 
IMPS GOMGTE MONS sina oe moons on essseoneeecedecsa eeacsoa=c0cers | 4 708 11 286 
SCOMG! SOME NO Ms non aessencsansso sor soe nonseaasbcassoasacces= | 5 1, 272 8 479 
{Noni TGA ION. = Gaooubasoss6dbabncdb ede coudoeseenossadodunEDs) 12 413 4 422 
JSCRIEGS TOE GD iMEMES (Cinw7O REASONS) baa aos seco s SoU eR oS uaEEans aes coo ee ona cons asdadesenoseadsecerer 459 
Some females laid no eggs and others only one or two groups, but 
these are included in the above averages. The average for all females 
as given is probably low, for in nature some of the overwintered 
females may have deposited eggs the preceding fall, and some of the 
third and fourth generation females, and a very small number of the 
second generation, might have deposited eggs the ensuing spring. 
Of 15,804 eggs laid in cage tests in 1921, 46.7 per cent hatched. 
Of 7,024 eges deposited in 1922, 52.5 per cent hatched. The lower 
ercentage in 1921 was due in part to the very low percentage of eggs 
ishing which were laid during the high temperature of August. 
The Mexican bean beetle is polygamous. A single fertilization of 
the female is sufficient for the production of as many as 10 groups of 
fertile eggs, even though five months or more passed in hibernation 
intervene between mating and the first egg deposition in the 
spring. (See Table 1.) Gravid females may thus enter hibernation 
and without further intervention of the male deposit fertile eggs in 
the spring. The beetles always feed on foliage in the spring before 
oviposition. 
The young larve hatch from the eggs after from 5 to 14 days, 
depending upon temperature conditions, the average incubation 
period at Birmingham, Ala., durmg June, July, and August being 
6 days. Hatching of all eggs in a group usually occurs within 24 
hours. The newly hatched larve leave the eggshells and cling te the 
tips of the eggs, completely covering the shells. They begin to feed 
soon after leaving the eggs, many of them reaching the leaf and feeding 
while clinging to the eggshells about the edge of the group. <A very 
thin layer of epidermis is eaten. After a day or so the larve begin 
to scatter and feed more heavily, devouring thicker portions of the 
leaf. By the time of the first molt they have scattered over several 
leaves. As they grow older they feed heavily and more rapidly 
and scatter over the plant or adjacent plants. In the third and fourth 
larval instars the most serious damage is done to the crop. 
The larve (Pl. IV, C) remain on the plant on which they have 
hatched, or on adjacent plants. While capable of crawling a con- 
siderable distance under adverse conditions, as much as 24 feet in 20 
minutes, migrations do not usually occur except prior to pupation 
when sufficient protection is not at hand. 
The larva’s method of feeding is characteristic of the species. 
(Pl. V, A, B.) It consumes a narrow band of the leaf and usually 
leaves the upper epidermis intact. It then moves and consumes 
another strip, and so on until several such parallel strips have been 
