316 



ENTOMOLOGICAL NEWS. 



[Jan 



flattened mushroom head, or thick plate, resting above the 

 other eye. In the males the dorsal, large faceted eye is much 

 smaller and less conspicuous than in the female, but both 

 parts of the eye (or botheye?) are plaiul y present. This dif- 

 ference in the two parts of the eye is more radical, however, 



than can be discovered 

 kya mere examination 

 from without. The 

 ommatidia or eye ele- 

 ments of each of the 

 regions differ, as shown 

 sections (see Fig. 

 5), in many particu- 

 lars. Corresponding 

 with the difference in 



-V 



size of the facets (the 



FIG. 5. Blepharocera capitata Loew, section of head COmeal leUSCS OI the 

 through the eyes; b., brain; o., ocelli; o. /., optic , firHrA flior-o i Q 



lobe ; /./., large faceted eye ; s.f., small faceted eye ; /, Ommaiiaiaj ineie 

 uufaceted region between the two eyes of each side. marked difference in 



the diameter of the ommatidia from the two regions. The 

 ommatidia of the dorsal large faceted eye are nearly twice as 

 wide and they are tully twice as long as the ommatidia 

 of the small faceted eye. Another striking and im- 

 portant difference is this, the larger ommatidia are very 

 much less strongly pigmeuted than the smaller ommatidia. 

 There are, also, some differences in the character of the inner 

 optic i ' layers ' ' lying between the hypodermal portion of the 

 eye and the brain; characters too technical for discussion 

 here. In sum, however, it is evident that there is so marked 

 a difference in structure between the two eye regions that 

 there must be a difference in function. The seeing by one of 

 the eye regions differs from the seeing by the other eye region . 

 In a brief discussion elsewhere of the ' i divided eyes of 

 arthropods " * I have referred to the observations of Chun,f 



* Kellogg. " The Divided Eyes of Arthropods," Zoologisches An- 

 zciger, 1898, No. 557, pp, 280-231. 



t Chun, Carl. "Atlantis, Biologische Studieu uber pelagische 

 Orgauismen," in Bibliotheca Zoologica, 1896, Bd. 7, Heft 19. 



