INTERDEPENDENCE OF ORGANISMS 43 



Hymenopterous gall makers belong, with a few exceptions 

 to two families, Tenthredinidae, saw flies, and Cynipidae, 

 gall wasps. Sawfly larvae make rather simple closed galls, 

 which they abandon when grown, to find some other place 

 of transformation. Gall wasps are gall makers par excel- 

 lence. They cause the most perfect nucleated galls: as a 

 family they are most completely adapted to the gall making 

 habit.* 



The tenants found in the course of the following study 

 occupying the galls collected, may be identified by the stu- 

 dent himself. For the adults, of which few, if any, will be 

 found, use the keys of any good manual of entomology. 

 Pupae if found may easily be reared. Place them uninjured 

 in a glass jar, add a wet sponge, or bunch of cotton to pre- 

 vent drying up, and tie netting (preferably fine swiss) over 

 the top of the jar, and let them stand till they emerge as 

 adult insects. Larvae, which will generally be found, may 

 be identified as follows: 



Key to the commoner insect larvae and mites found in galls. 



A. Body short and thick: legs rather long. 



B. Head fused with body and not distinct; legs 2 or 4 



pairs Acarina, Mites. 



BB. With distinct head: legs 3 pairs (Hemiptera). 

 C. Wing pads present, projecting at right angles with 

 the body: no cornicles on abdomen. .Psyllidae. 

 CC. Wing pads absent, or if present, laid lengthwise of 

 the body: cornicles often present (see fig. 39).Aphidae 

 AA. Body cylindric, worm-like: legs minute or none. 

 B. With 3 pairs of minute legs under the thoracic seg- 

 ments. 



*It is to be observed that there is not a single family of insects 

 whose members are all gall makers: Cynipidce comes nearest. 



