453 



were favourable for the development of the bug, but the numbers were 

 much below the average. The average parasitism at Manhattan during 

 the summer was 32 per cent, and during the spring, when chinch bugs 

 were most numerous, ranged from 20 to 40 per cent. The period of 

 oviposition of the bug covered about two months, while the life-cycle 

 of the parasite extended over a period of 2-3 weeks. Thus, the eggs 

 of a single bug were exposed to about three broods of parasites. 

 A description of the external characters of the egg, larva, pupa and 

 adult is given. The larva reaches its full development in about six 

 days ; by the end of this time the egg of the host is completely 

 destroyed. The pupal stage lasts from 11 to 13 days. The number of 

 eggs laid by the adult females varies between 20 and 40 each. The 

 female cannot distinguish between parasitised and non-parasitised 

 eggs and double parasitism often results. If this occurs, it results 

 in the death of both larvae. If the second parasitism takes place 

 while the first parasite is in the pupal stage, the second parasite 

 does not develop. E. henejica can reproduce partheno-geneticaUy, 

 but sexual reproduction seems to be the rule. The parasites 

 show a preference for chinch bug eggs which are from 1 to 3 days old. 

 The length of adult life varies from a few hours to 78 days ; low 

 temperatures have the effect of increasing the duration of the adult 

 stage. The period of activity lasts from the beginning of May to the 

 end of November. Nine generations have been raised in a year. The 

 effect of feeding is not appreciable in the length of hfe or oviposition. 

 The adults show negative phototropism, and in the field are often 

 found between the leaf -sheath and stalk of plants or in small cracks 

 in the ground. 



McCoNNELL (W.R.). A unique Type of Insect Injury. — Jl. Econ. 

 Entom., Concord, vii, no. 2, April 1915, pp. 261-267. 



Cerotoma trifurcata, the bean-leaf beetle, is chiefly known from the 

 damage done by the adults to the foliage of beans and cowpeas ; 

 the larvae have been described as feeding on the roots and bark of 

 the subterranean part of the stem. In 1912, the nodules of the roots of 

 cowpeas were found to be damaged by larvae resembling those of 

 Diabrotica. These proved on examination to be those of C. trifurcata ; 

 they were most destructive on poor soils where soil enrichment through 

 the growth of a leguminous crop was important. The food-plants of 

 the beetle comprise bush and pole beans, co^vpeas, bush clover, 

 Meihomia sp., Faha sp., etc. The insect is distributed over the eastern 

 part of the country from New York to Minnesota and southward to 

 Kansas and Mexico. The life-history is as follows. The adults emerge 

 from their hibernating places in the spring ; after feeding for a week 

 or more on garden beans or native food-plants, they deposit eggs in 

 the soil within a few inches of the base of the plants. Oviposition 

 continues for several weeks. The eggs hatch in about 18 days in spring. 

 The larvae feed on roots, root hairs and nodules. The entire contents 

 of the latter are devoured. Pupation takes place in the soil near the 

 base of the plants at a depth var}nng from 1 to 3 inches. The larval 

 period varies from 3 to 6 weeks, while the pupal stage lasts about 4 days 

 in summer and 1 to 2 months in autumn. The first generation appears 



