ANATOMY. 



27 



EYES. 



The compound eyes are composed of a large number of ommatidia, 

 closely packed together. According to Zeleny and Mattoon (1915), 

 each eye of D. melanogaster is made up of about 700 ommatidia. 

 These have hexagonal outlines, as viewed from the surface. At 

 alternate angles of each hexagon there is a minute hair, i. e., each 

 ommatidium has three hairs next to it. The size and color of these 

 hairs is characteristic for each species. In at least some species of 

 Chymomyza there is an area of enlarged ommatidia in the lower anterior 

 part of the eye; in general, however, the ommatidia do not differ 

 appreciably in size in any one eye. 



The ocelli, or simple eyes, are three in number. They are situated 

 near the vertex, between the compound eyes. There is a median 

 anterior one, and a lateral posterior one on each side. 



THORAX. 



The thorax is made up of three fused segments; prothorax, meso- 

 thorax, and metathorax. Each bears a pair of legs, the mesothorax 

 bears the wings, and the metathorax the halteres. 



Prothorax: The dorsal aspect of the thorax is made up almost entirely 

 of mesothorax. Only the two anterior lateral angles are prothoracic, and 



Fig. 7. — Side view of thorax of Drosophila funebris (diagrammatic). Abd, abdomen; 

 Ci, C2, Cz, coxae; ds, dorso-central bristles; H, head; Ha, haltere; Hp, 

 hypopleura; Hu, humerus; Mn, mesonotum; Ms, mesopleura; Mt, meta- 

 notum; n-p, notopleural bristles; pa, postalar bristles; Pp, propleura; 

 ps, presutural bristle; Pt, pteropleura; Si, S2, thoracic spiracles; sa, supra- 

 alar bristles; Sc, scutellum; St, sternopleura; Ts, transverse suture; W, 

 base of wing. 



