4 8 



ENTOMOLOGY 



cence proceeds towards the base of the wing." (Comstock and Needham.) 

 The former, or outward, kind of coalescence is common in most orders of 

 insects; the latter, or inward, kind is especially prevalent in Diptera. 



Specialization by addition occurs by a multiplication of the branches 

 of the principal veins. 



Comstock and Needham have succeeded in homologizing practically 

 all the types of neuration, including such perplexing types as those 



of Ephemerida (Fig. 70), 

 Odonata (Fig. 20, B) and 

 Hymenoptera (Fig. 71), 

 and their thorough work 

 affords a sound basis for a 

 rational terminology of the 

 wing veins; there is no 

 longer any excuse for the 

 lamentable confusion that 

 has hitherto attended the 

 study of venation. 



Folding of Wing. In 

 some beetles (as Chrysobo- 



thris) the wings are no larger than the elytra and are not folded; in others, 

 however, the wings exceed the elytra in size, and when not in use are folded 

 under the elytra in ways that are simple but efficient, as described by 

 Kolbe and by Tower. To be understood, the process of folding should 

 be observed in the living insect. As described by Tower for the Colorado 



FIG. 70. Wings of a May fly. Lettering as before. 



FIG. 71. A typical hymenopterous wing. Lettering as before. 



potato beetle, the folded wing (Fig. 72, B) exhibits a costal joint (a), a 

 fold parallel to the transverse vein (6), and a complex joint at d. The 

 wing rotates upon the articular head (ah) and when folded back beneath 

 the wing-covers the inner end of the cotyla (c) is brought into contact 

 with a chitinous sclerite of the thorax, which stops the further movement 



