V 



>? 



•384 w. wesche on structure of eye-surface in diptera 



Explanation of Plate 28. 



Fig. 1. Portions of the eyes of a Cecidomyid, highly magnified. 

 The section drawn is on the top of the head, and 

 shows parts of both eyes, the bare area in the 

 middle being the median line. 



2. Head of Bibio hortulanus, L., ^, drawn at a low 

 magnification. A lateral view is given ; a in- 

 dicates the situation of the lower eye. 



3. Part of an eye of Sciara thomae, L. To show the 

 chitinous plate pierced with round apertures for the 

 lenses, and the short pubescence characteristic of 

 the Mycetophilidae. 



,, 4. Edge of the eye of an undetermined Sciara, to show 



the hyaline structure of the lenses. 

 „ 5. Part of an eye of Bilophus febrilis, L., $ , showing the 



larger facets. 

 „ 6. The smaller facets on an eye of Simulium ornatvm, 



Mg\, ^, drawn to the same scale as Fig. 7, and for 



comparison with it. 

 ,, 7. The larger or upper facets of Simulium ornatum, <$ . 

 „ 8. Part of an eye of Haematojmta pl/u/oicdis, L., <$ , showing 



the chitinous lower structure with smaller facets, 



and the transition area merging into the larger 



facets, where the opaque structure is obliterated. 

 „ 9. Part of an eye of Tijmla oleracea, L. 



10. Part of an eye of Calliphora erythrocephala, Mg. 



11. Part of an eye of Chironomus dorsalis, Mg., showing 

 the upper portion of the plate where it bends round 

 the antennae. 



„ 12. Part of a double eye of Dilophus nigrostigma, Hutton, 

 J, a New Zealand Bibionid. To show the chitinous 

 structure separating the upper from the lower eye. 

 The larger lenses are in the upper eye. 



„ 13. Edge of the eye of Bibio hortulanus $ , to show the 

 pubescence, which is, however, often much thicker, 

 as hairs not socketed in the field of vision have 

 been omitted. 



1 ■ — 



Joi'i-a. Quekctt Microscopical Club, Ser. 2, Vol. X., No. (34, April 1909. 



>> 

 ?> 



