494 EXTERNAL ANATOMY OF INSECTS. 



Lepisma, the Tulidte, and several of the Scolopendridce. 

 In Scolopendra forjicata the eye consists of about twenty 

 contiguous, circular, pellucid lenses, arranged in five 

 lines, with another larger behind them, as a sentinel or 

 scout, placed at some little distance from the main body. 

 In the common millepede (lulus terrestris) there are 

 twenty-eight of these eyes, placed in seven rows, and 

 forming a triangle, thus .. : & — the posterior row con- 

 taining seven lenses, the next six, and so on, gradually 

 losing one, till the last terminates in unity. Each of 

 these lenses is umbilicated, or marked with a central de- 

 pression. In Craspedosoma Leach, you will find a similar 

 formation. In Glomeris zonata, a kind of wood-louse 

 that rolls itself into a ball, the lenses are arranged in a 

 line curved at the lower end, with a single one by itself 

 at the posterior end on the outside; they are oblong and 

 set transversely, and their white hue and transparency 

 give them the appearance of so many minute gems, espe- 

 cially as contrasted with the black colour of the animal 3 . 

 Between these eyes and the antennae is another trans- 

 verse linear white body, but opaque, seemingly set in a 

 socket, and surrounded by a white elevated line, like the 

 bezel of a ring. Whether it is an eye, or what organ, I 

 cannot conjecture b . Its aspect is that of a spiracle. 



3. Compound Eyes z . — These are the most common kind 

 of eye in hexapod insects, when arrived at their perfect 

 state ; in their larva state, as we have seen, their eyes 

 being usually simple d ; except, indeed, those whose me- 

 tamorphosis is semicomplete, which have compound eyes 



* Plate XXIX. Fig. 1 1. h. •> Ibid. a. 



c Plate XIIT. Fig. 10. <i See above, p. 117— 



