44 GENERAL BIOLOGY 



C. With a brown shield covering the prothorax above: 



body armed with stiff bristles 



Lepidoptera, moth larvae. 



CC. Without a brown prothoracic shield. 



D. With rudimentary legs (pro-legs) underneath 



some of the abdominal segments 



Tenthredinidae, sawfly larvae. 



DD. With no abdominal prolegs 



Coleoptera, beetle larvae. 



BB. Legless. 



C. With a distinct head segment : body arcuate, white. 

 D. Body segments deeply wrinkled: head brown: 



skin dull white 



Coleoptera, Family Curculionidae, weevils. 

 DD. Body segments smooth, shining, head mostly 



white Cynipidae, gall wasp larvae. 



CC. With the head segment greatly reduced, very 



minute or wanting: body straight. . . .Diptera. 



D. With the ventral piece shown in fig. 34 Color 



often red or yellow. . .Cecidomyidae, gall gnats. 



DD. Without this structure. Color white 



Other dipterous larvae 



Despite the food, cover, and defense, provided by 

 the plant for the gall maker, the fact must not be lost 

 sight of that the creature is the plant's enemy. The 

 young bur-oak shown in figure 35 gives evidence of this. 

 Cynipid galls, growing too thickly have killed the ter- 

 minal shoot, and the lateral shoots are taking up the 

 growth. Such positive injury from galls is rarely seen, how- 

 ever, for the gall makers are kept in check by hosts of very 

 efficient parasites. The student following the field work 

 outlined below will be sure to come upon some of these 

 parasites, and it may be with some difficulty that he will 

 distinguish which is parasite and which is gall maker in 



