MECOPTERA. Yil 



The larva resembles a caterpillar in form, and in the 

 possession of three pairs of thoracic legs and abdomi- 

 nal prop-legs. In the caterpillar, however, there are 

 never more than five pairs of prop-legs, while Panorpa 

 has eight pairs. Besides the feet, there are warts on 

 the body provided with bristles. 



The snow-insect, Boreus,* also belongs to this order. 

 Here the prothorax is larger than in Panorpa. The 

 male of this genus has short wings covering only 

 about half of the abdomen, and so stiff as to be use- 

 less flying-organs, while in the female the wings have 

 wholly disappeared. 



The scorpion-flies have been described by Packard 

 in the volume so often quoted. He shows that while 

 the adult is more like the Neuroptera, the larvae, as 

 we have stated, are very similar to caterpillars, having 

 two-jointed abdominal legs, and four-jointed thoracic 

 legs, and suggests that the Mecoptera and Lepidop- 

 tera arose from the same stem- form. 



The general absence of a true Thysanuriform larva 

 in the development of Mecoptera and remaining 

 orders is a great and probably significant change. 

 It may indicate that these orders have not passed 

 through any Thysanuroid ancestral epoch, during 

 which their immediate ancestors were wingless and 

 similar to Thysanura! It is possible that they may 

 have been derived from some winged form similar to 

 Neuroptera, since this is older and more primitive 

 in its mode of development and presents transitional 

 characters in this respect as well as in the larvae of 

 some forms like Mantispa. 



1 For colored figure, see Westwood, Introd. Mod. Class. Ins.., 

 frontispiece, Fig. 3. 



