292 BEES AND WASPS 



culmination in the community habit of ants and bees. In 

 no other si'oup except the white ants is there such develop- 

 ment of the community habit. 



The pupa stage is generally included in the nest or cells 

 formed for the larval stage, and the forms are seen to be 

 quite highly speciahzed when the cocoon is cut open. The 

 larvffi moult but the moults are not so conspicuous as in 

 exposed forms. The group exliibits quite a variety of 

 habit, some leaf-eating forms, some wood-boring forms, 

 some that develop in galls, many that are parasitic inter- 

 nally on other insects, and many store food in their nests, 

 such as spiders, caterpillars, etc. These are sometimes 

 stored in the ground, sometimes in mud cells, sometimes in 

 channels in the wood, sometimes in paper cells. 



There are two large divisions, the Phytophaga, leaf-eating 

 or plant-feeding free caterpillar-like forms, and the Aculeata 

 wliich represent the other forms of the group, the larvje of 

 which are dependent on a food supply provided by the adult. 

 The adults of this group have a sting. 



The group T enihrediindoe is a large family of leaf-eating 

 and gall-making insects and the typical ones being the 

 willow saw fly and the gall-making willow forms. 



The willow saw fly {Cimhcx americana) is one of the largest 

 species that we have. The adult is steel blue, the wings 

 smoky. It is quite conspicuous and lays its eggs on the 

 leaves of the willow along the midrib and principal veins of 

 the leaf. The larvse hatch in a few days and grow during 

 the midsummer and are noticed as large yellow^ caterpillar- 

 like forms clinging to the twigs and leaves of willow par- 

 ticularly or sometimes also to elms and a few other kinds of 

 of trees. Some of the larvae have a prominent black dorsal 

 line. They coil themselves quite a little especially when 

 resting. While feeding the body is stretched out and they 

 cling by means of the prolegs of the abdomen as well as by 

 the thoracic legs. Prolegs are similar to those of the cater- 

 pillar. There are certain similarities with some of the very 

 generalized Lepidoptera and the prolegs might possibly be 

 taken to indicate some affinity. However, it is probably 



