TYPE TRACHEATA. 



519 



The larvae of the Tenthredinidae, for example that of the 

 Pear-slug (Selandria), which feeds upon the leaves of the pear- 

 tree, resemble the caterpillars iu possessing prop-legs, of 

 which there are as many as eight pairs. In the majority of 

 forms, however, owing to parasitism or to being in contact 



FIG. 243. Sphex icfineumonea (from PACKARD). 



FTG 244. Hypoderma boms (from PACKARD). 



with an abundant supply of nutrition stored up by the parents 

 (Bees, Wasps) or to being fed and cared for by the workers 

 among the Ants, the larvae are maggotlike and almost or 

 entirely destitute of legs. The metamorphosis is complete, 

 the pupa being a pupa libera. 



15. Order Diptera. 



In this order, as the name indicates, but two wings are 

 present (Fig. 244), which are those of the mesothorax, the 



