Evobdion and Taxonomy 95 



greatly. In certain cases where the body of the insect has be- 

 come greatly reduced in size, a reduction of the area of the 

 wing membrane has taken place and correlated with this there 

 has been a great expansion of the fringe of the wing. The 

 best known examples of this are the narrow-winged Tineids, 

 the Thysanoptera, and certain parasitic Hymenoptera. This 

 kind of specialization seems possible only with minute in- 

 sects, where the weight to be supported during flight is not 

 great. 



In a Tineid which I have studied the hairs composing the 

 fringes of the wing are inserted in the lower side of the wing- 

 membrane a short distance back from the edge of the wing ; 

 and the edge of the wing is stiffened above hy strong over- 

 lapping scales. This arrangement renders the fringes rigid 

 during the downward stroke of the wing, but admits of their 

 depression during the upward stroke ; a combination well 

 adapted to facilitate flight. 



The second method of specialization referred to above is the 

 loss of the front wings in the Coleoptera and Euplexoptera. In 

 these two orders the paraptera of the mesothorax have been 

 developed into elytra, and have crowded out the front pair of 

 wings. The function of flight has been relegated in this way 

 to the hind wings. 



This homolog}' of the elytra of beetles with the tegulae of 

 Hymenoptera and with the patagia of Lepidoptera was point- 

 ed out by F. Meinert long ago* ; but Meinert's paper seems 

 to have escaped the attention of entomologists almost entirely. 

 It is referred to by C. Hofifbauer in his paper on the minute 

 structure of the elytra, f But although Hoffbauer shows 

 conclusively that the structure of the elytra resembles that of 

 the pronotum and differs in every essential feature from that 

 of the wings, strangely enough he does not accept the conclu- 

 sion of Meinert. 



Meinert also pointed out the fact that in many Coleoptera 

 {e. g. , Dytiscus) rudiments of the front wings exist beneath 

 the elytra. 



*Entomologisk Tidskrift, 1880, 168. 

 tZeit. Wiss. ZooL, LIV, {1S92,) 579. 



