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 botheyes) are plainl y present. This dif- 

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



than can be discovered 

 by a mere examination 

 from without. The 

 ommatidia or eye ele- 

 ments of each of the 

 regions differ,as shown 

 [.jQ6by sections (see Fig. 

 5), in many particu- 

 - lars. Corresponding 

 ^' with the difference in 

 _ ~ i r size of the facets (the 



Fio. 5. ^/^■/^Aa'''«<f^a'^a/'''^^'^ I-oew, section of head corneal ICUSCS of the 

 tbrouKh the eycH; A., brain; o., ocelli; o. /., optic ^»„,^„4-:/i;„\ ^x.a.va. 4o q 

 lobe ; l.f., larite faceted eye ; sj., small faceted eye : t, Ommaiiaia; LUere ih d. 

 nafaceted rcKlon between the two eyes of each side. jjjr^j.]-g(J 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 pigmeute<l than the smaller ommatidia. 

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

 optic ''layers" lying l>etwe<;n the hypodennal portion of the 

 eye and the brain; chanujters t^w) technicjil for discussion 

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

 a diflTcrence in Mtructnre iHJtwwMi the two eye regions that 

 there muut lie a difference in functtion. The seeing by one of 

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

 In a brief iliwMiHsion elwjwhere of the " divided eyes of 

 arthropodM " * I have referre<l to the observatiims of Chun,t 



* Kellogg. " The DIrided Eye* of Arthropods," Zoologisches An- 

 selger, 1806, No. M7, pp, 28()-28l. 



t Chun, Ctrl. "Atlnntin, Biolo{fiHche Studien ubor pelatfische 

 OryftoUnnen," in Bi>>nothoca Zoologica, 1896, Bd. 7, Heft lu. 



