December, '16] watson: velvet-bean caterpu.lak 527 



great flocks composed largely of immature individuals. Other birds, 

 especially mocking-birds and field sparrows, feed eagerly upon them. 

 The lizard Anolis ("chameleon") is also an important enemy, which 

 is commonly seen climbing over the vines. Various species of wasps 

 prey upon them. Callida decora, a small blue carabid, is common on 

 the plants and feeds upon the eggs as well as the young larva?. Next 

 to the blackbirds the most important predaceous enemies are probably 

 several species of hemiptera. Alccvorrhynchus grandis Dall., is prob- 

 ably the most abundant but Brochymena annulata Fab., and Eurhy- 

 rhynchus floridensis Linn., and Podisus maculiventris Say are common. 



In sharp contrast to the predaceous enemies the insect is remarkably 

 free of internal parasites. From many hundreds of pupae collected but 

 two parasites were raised. One (PI. 39, fig. 5) proved to be an undescribed 

 species of Tachinid which Townsend has named Euphorocera floridensis 

 and the other an ichneumon, Itoplectis rufuscida Davis (PI. 39, fig. 6). 



Cholera. — By far the most efficient check on the increase of this 

 insect is a disease of the caterpillars called "cholera" by the farmers. 

 It is caused by a fungus, Botrytis rileyi. Sometime during September 

 ■or early October this has always become epidemic in the fields and in a 

 week's time all but exterminated the caterpillars, a very small fraction 

 of one per cent escaping. After the epidemic one may have to search 

 for an hour or more to find a single live caterpillar where a week before 

 they had been so numerous as to strip most of the leaves from the 

 vines. 



The first symptom of the disease is the flaccid, emaciated appearance 

 of the caterpillar. It does not feed. It soon elevates the anterior 

 portion of the body, head, thorax and first two abdominal segments at 

 an angle of about 4.5 degrees and dies in that position (PI. 39, fig. 3). In 

 a day or two the spores mature and the corpse turns white. Healthy 

 caterpillars confined with these corpses become sick in three days. 

 The fungus attacks all instars alike. Although it is usually possible 

 to find a few of these nmmmics in the field at any time during the cater- 

 pillar season, it requires favorable weather conditions to start the 

 epidemics. These conditions seem to be a prolonged and rather cool 

 rain such as frequently occurs in late September. Perhaps the resist- 

 ance of the caterpillars is lowered by the cooler weather as this is a 

 distinctly subtropical insect. At least we have not succeeded in our 

 attempts to start a premature epidemic. Even when the caterpillars 

 were confined under a bell-jar in a saturated atmosphere with mum- 

 mies, the disease did not become epidemic among them until "cholera 

 time" arrived. 



Although there may be a partial recovery after an epidemic, the 

 caterpillars never again during that season become sufficiently numer- 



