28 BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 



host was hibernating as an adult, and this habit may make coloniza- 

 tion difficult. This parasite appears to be capable of immense 

 benefit. 



Phytophagous Coccinellidae in Java, according to Dr. P. van der 

 Goot, entomologist to the Dutch Government, are attacked in the 

 egg, larva, and pupa stages by Hymenoptera; hence it appears that 

 other parasites that may prove useful against Epilachna corrupta 

 may be found. 



EFFECT OF SUNLIGHT. 



During a prolonged hot dry period in 1921, when bean beetles were 

 so numerous that they destroyed all bean plantings in the Birmingham 

 district, the larvae were forced to crawl about in search of food, and 

 were also exposed to the sun on the stems and stalks of plants. Pupae 

 were so numerous that many stalks and pods were literally covered 

 with them, and many larvae pupated on the ground, or on stones, 

 weeds, or any object at hand. Many thousands of pupae gradually 

 turned brown and died. 



Experiments were performed and various stages of the insect were 

 exposed to sunlight. The eggs, which are normally protected from 

 direct sunlight, are occasionally laid on the upper surface of the leaf, 

 or, when laid on the under surface, may be exposed in some in- 

 stances by bean leaves growing upward. This is often the case with 

 the tepary bean. An exposure to sunlight for 33 hours on four con- 

 secutive days in June killed 57 eggs when the shade temperature 

 ranged from 74° to 94° F., but 15 eggs of a group of 59 hatched after 

 30 hours' exposure on the same days. Twenty-four groups, totaling 

 1,240 eggs, exposed to the sun continuously from three to five days 

 during late July and August at shade temperatures reaching a maxi- 

 mum of from 80° to 101° F., succumbed with the exception of two 

 eggs. 



An exposure to direct sunlight for two minutes was fatal to first- 

 instar larvae 1 day old when shade temperatures registered 96° F. 

 Second-instar larvae, 5 days old, succumbed after seven minutes' 

 exposure to direct sunlight when the shade temperature registered 

 92° F. Third-instar and fourth-instar larvae succumbed after 10 

 minutes' exposure to direct sunlight when the shade temperature 

 registered 93° F. 



Three hundred pupae were collected in the field September 12 and 

 exposed to the sun for two days when maximum shade temperatures 

 each day registered 96° F., and all succumbed, while 78 per cent of 

 a check of 100 pupae emerged in the shade, and all pupae reared in 

 the shade in other experiments emerged. Undoubtedly most of the 

 22 per cent of pupae of the check lot had been killed by sunlight in the 

 field. 



Adults are more resistant, and since they can fly to sheltered 

 places are not usually killed by effect of sunlight. Under conditions 

 of light or medium infestation, large numbers of the various stages 

 of the insect are not exposed and no great benefit from this source 

 occurs. All in all, however, the factors enumerated above, and no 

 doubt others which were not observed, tended to reduce the 

 number of adults going into hibernation to such an extent that the 

 infestation was much lighter in 1922 than in 1921. 



