THYSANURA 



185 



Blattidae ; Grassi states, however, that not only are they eyes, 

 but that they are of almost unique structure, being, in fact, 

 intermediate between simple and compound eyes. 



The mode of development of the compound eyes of MacJiilis 

 is of considerable interest, but unfortunately very little is known 

 about it, even the period at whicli the eyes appear being uncertain. 

 Judging from analogy with the^ Orthoptera, we should suppose 

 them to be present when the Insect leaves the egg, and Oudemans 

 apparently considers this to be the case, but Bolivar states ^ that 



Fig. 92. Head of Machilis mari- 

 timet (after Oudemans) : A, base 

 of antenna ; C, clypeus ; F, ver- 

 tex ; P, fold ; 0, eye ; 0, 0', sup- 

 posed simple eye ; M, mandible ; 

 m, maxilla ; L, upper lip ; I, lower 

 lip ; T, portion of maxillary palp ; 

 t, of labial palp. x 20. 



Fig. 93. Lepisma cincta. (After 

 Oudemans.) x 4. (The line indi- 

 cates the natural length. ) 



in the early stages of Maclnlis the eyes are only simple eyes ; 

 these being replaced by compound eyes in the later life. The 

 writer has observed very young individuals of Machilis polypoda, 

 and found the eyes to be evidently compound. 



The remaining family of Thysanura, the Lepismidae, is in 

 certain respects the most highly developed of the Order. The 

 covering of scales found on the body is very remarkable in some 

 of the species, especially in the genus Lepisma (Fig. 93, /^. 

 cimta) ; the thoracic segments are different from one another 

 1 Ann. Soc. ent. France, 1892, p. 34. 



