SOME REPRESENTATI\^ INSECTS 



379 



The larvae of caddis-flies (Tricoptera) are of interest because 

 of the tubes that they construct by fastening together bits of debris 

 with silken threads which the larva spins. In locomotion the 

 head and thoracic segments, with their legs, are extended and 

 the animal crawls along the bottom of the stream, dragging its 

 tube. When disturbed it withdraws and hes motionless. 





w 



Fig. 134. — Life cycle of the Harlequin cabbage bug. Murgantia histrionica, 



one of the Order Hemiptera. 



a, adult; 6, egg mass; c to g, larval stages. (From Farmers' Bulletin, No 1061, U S. 

 Dept. Agr.) 



Hemiptera. — The squash-bug, Anasa tristis (cf. Fig. 194), which 

 is a pest upon squash and pumpkin vines the country over, is per- 

 haps known best by its disagreeable odor. It is representative of 

 the true " bugs " with its sucking mouth parts and the wings 

 showing the X-shaped pattern that is characteristic of so many 

 Hemiptera. The adults hibernate over the winter, dying in the 

 spring soon after the eggs are laid upon the tender sprouts of the 

 vines where the young are destined to feed. The development, 



