60 EN TOMOLOGY 
and the absence of the base of the media in Anosia (Fig. 69) 
and many other Lepidoptera; in the pupa of Anosia, the media 
may be found complete. Coalescence “takes place in two ways: 
first, the point at which two veins separate occurs nearer and 
Fic. 68. 
Wing of a fly, Rhyphus. Lettering as before. 
nearer the margin of the wing, until finally, when the margin 
is reached, a single vein remains where there were two before; 
second, the tips of two veins may approach each other on the 
margin of the wing until they unite, and then the coalescence 
Fic. 609. 
Wing of a butterfly, Anosia. Lettering as before. 
proceeds towards the base of the wing.”’ (Comstock and Need- 
ham.) The former, or outward, kind of coalescence is com- 
mon in most orders of insects; the latter, or mzvard, kind is 
especially prevalent in Diptera. 
Specialization by addition occurs by a multiplication of the 
branches of the principal veins. 
