326 STATES OF INSECTS. 



two-winged flies, the male eyes meet at some point below 

 the stemmata, and above the antennae. In the former 

 they touch more at an angle ; for the vertex forming a 

 narrow isosceles triangle, and for the anterior part of the 

 face one nearly equilateral : while those of the female are 

 separated by a considerable interval. In Heptatoma 

 and Hcematopota in that sex, a similar interval obtains ; 

 while in the other, after forming a minute short triangle, 

 they unite for a considerable space, and then diverging, 

 form the face. This is also the case in Tabanus ; but in 

 the female, the space that intervenes between the poste- 

 i"ior part of the eyes is much narrower than in these two 

 cognate genera of the horse-flies. In some others of 

 this order, as Musca Latr., the eyes of the male do not 

 touch, but approach posteriorly much nearer to each 

 other than those of the other sex. In a few instances 

 the sexes vary even in the number of their eyes, as well 

 as the size. This occurs in some species of Ephemera L. 

 (E. diptera, &c), in which the male, besides the com- 

 mon lateral ones, has two large and striking interme- 

 diate eyes, that sit upon vertical pillars or footstalks 3 . 



2. The Trunk, The thorax of many coleopterous 

 males, especially of the Dynaslidce and Copridaz amongst 

 the petalocerous tribes, exhibits very striking differences 

 from that of the female. In many Lucani the lateral 

 angle is more prominent. In Antliia it is bilobed poste- 

 riorly, while in the last-mentioned sex it is entire b . In 

 Phanasus carnifcx MacLeay (Copris F.) it is elevated into 

 a plane triangular space, with the vertex of the triangle 



• Plate XXVI. Fig. 33. De Geer ii. 651. 659. 

 b Voet Colcopt. I f. xxxix.f. 47, 48. ?. . 46. $ . 



