410 SYNOPTIC COLLECTION. 



found on the pelican, and which is related to Nirmus 

 daviformis Denny (PI. 998, fig. i), and to the common 

 hen-louse, Menopon pallidum Nitzsch (the colqr of the 

 last species is shown in figure 2 of PI. 998, while the 

 details of structure are better seen in PI. 999). Accord- 

 ing to Kellogg, 1 to whom we are indebted for most of the 

 facts in this description, the eggs of Lipeurus are fastened 

 singly to the vanes of the feathers of the host, and the 

 young (PI. 997, fig. i) is a parasite at start. Its head is 

 large in proportion to the size of the body, and the tho- 

 rax, even at this early stage, is apparently made of only 

 two segments, the mesothorax and metathorax being 

 united without visible suture. This union is doubtless 

 a vestige of the time when the insect possessed two pairs 

 of wings and was a flier ; it is also a proof that Lipeurus 

 is a secondary and not a primitive animal. 



In the main, the young (fig. 2, an older stage) and the 

 adult (fig. 3, 9 ; fig. 4, $~) resemble each other. This 

 resemblance, however, cannot be compared with the re- 

 semblance of the larval and adult Thysanura, since in 

 this case of the Mallophaga we have not primitive sim- 

 plicity but on the contrary a specialized larva fitted for 

 a parasitic life. The body is extremely flattened and 

 hardened by chitin. The biting mouth parts are modi- 

 fied for cutting feathers or hair, bits of which are seen 

 in the crop through the seinitransparent walls of the body. 

 In some species the upper lip serves as a scraper and the 

 mandibles are provided with sharp teeth. The feet ter- 

 minate in claws for clinging, while the fore legs are used 

 as foot-jaws for carrying food to the mouth. 



The wing muscles are greatly reduced in size and there 

 are no indications of wings in any stage of any species 

 of the group. 



While it is true that these insects are parasites, they 



1 Leland Stanford Junior Univ., Contrib. Biol. Hopkins Seaside 

 Lab., IV, 1896. 



