PEA AND BEAN INSECTS 



63 



The Cowpea Weevil 



Bruchus chinensis Linnaeus 



Beans and peas in the southern states often become infested 

 by the cowpea weevil. This insect is widely distributed through- 

 out the tropics. In the United States its range extends north- 

 ward to Maryland and Iowa. The 

 beetle (Fig. 46) is from yV to y inch 

 in length, brownish in color and may 

 be distinguished from the other 

 species in this country by the two 

 ivory-white spots on the middle of 

 the hind margin of the prothorax. 

 The wing-covers are brownish, dark 

 at the base and usually crossed 

 with a darker band at the middle. 

 In the male the antennje are pec- 

 tinate. 



The female glues her eggs on the outside of the pods. The 

 egg is ovate, flattened on the side of attachment, translucent, 

 about ^V ii^<^'l^ ii^ length by -^ in width. The eggs hatch in 

 four to ten days and the young larva bores through the pod 

 and enters the seed. In the field, the larvae become full-grown 

 in two or three weeks in midsummer. They closely resemble 

 those of the bean weevil and several larvae may infest a single 

 seed. Pupation takes place within the seed and transforma- 

 tion to the beetle occurs in four or five days in warm weather. 

 Breeding continues in stored seeds and six or seven broods 

 may develop annually in the District of Columbia. 



46. — The cowpea 

 weevil (X S). 



References 



U. S. Div. Ent. Bull. 8, pp. 24-27. 1897. 

 U. S. Bur. Ent. Bull. 90, pp. 83-94. 1912. 



