DIPTERA 



397 



FIG. 281. Hessian-fly galls on wheat stem h, and healthy wheat at left, a, egg; b, 

 larva; c, "flaxseed" or winter stage of larva; d, pupa; /, adult female; g, adult male; t, the 

 parasite which often destroys the Hessian-fly or holds it in check. (Economic Entomology.) 



