LEPIDOPTERA. 



231 



Fig. 165. 



are also characters which show that they are more degraded than 

 the Hymenoptera. There is also a greater disproportion in the 

 relative size of the three thoracic rings. In the abdominal rings 

 the pleurites are much larger than in Hymenoptera, where they 

 are partially obsolete. They 

 scarcely use the legs, the fore 

 pair (so remarkably differen- 

 tiated in the higher Hymenop- 

 tera) being partially obsolete 

 in some butterflies (Vanessa, 

 etc.). They are essentially 

 fliers, not having the great 

 variety in the mode of loco- 

 motion observable in the Hymenoptera. No parasites are 

 known to occur in this suborder. They are only social while in 

 the larval state, and then merely because their eggs, in such in- 

 stances, are laid in bunches, and on distinct food-plants to 

 which the larvae are confined. The adults rarely 

 take an active part in the economy of nature, 

 and have but little opportunity for the mani- 

 festation of instinct and reason, though the 

 larvae in seeking for suitable places in which 

 to undergo their transformations often exhibit 

 wonderful instinct. 

 The readiest method of determining the natural position of 

 groups is by a comparison of their degradational forms.- Thus 

 we find that in the degraded Hymenoptera the tripartite form 

 of the body is preserved ; Avhile, on the contrary, in the Aving- 

 less Lepidoptera (such as the female 

 of Orgyia and Anisopteryx) the body 

 is either oval, the head being less 

 free and smaller than in the Avinged 

 form, and the thorax and abdomen 

 continuous, their respective rings 

 being of much the same size and 

 shape, while the legs are feeble : 

 or, as in the female of (Eketicus, 

 the body is elongated, and worm-like. The wingless moths, 

 then, are much lower than the worker ants, the female Scolia, 



Fig. 166. 



K!7 



