The Hog Louse 673 



maxillae as the bristles lying within it. Graber (1872:138) distinguished 

 in the mouth parts of Phthirius an upper lip, an under lip (proboscis), 

 and a sucking tube formed possibly by the fusion of the mandibles and 

 the maxillae and capable of protrusion from the prolDoscis, but he did 

 not realize the true nature of the piercers and their sheath. He saw 

 these structures extending far back in the ventral region of the head, 

 and interpreted them as the retractor muscle of the proboscis. 



The next two in the long succession of publications appeared at intervals 

 of ten years, and both dealt, one entirely and the other in part, with species 

 affecting domestic animals. Strobelt (1882, EngUsh trans. 1883:86) de- 

 scribed very incompletely some of the structures surrounding the mouth 

 openings of Linognathus vituli (Haeniatopinus tenuirostris) without seeing 

 the real mouth parts, while Meinert (1891-92:58) used Haematopimts 

 suis to illustrate his study of the mouth parts of Pedicidus humanus 

 and figured the different parts of the apparatus. Meinert called the 

 whole structure the pharynx, distinguishing the anterior part of the 

 stomodaeum proper as the epiph^rynx and the ventral sheath and piercers 

 as the hypopharynx. 



A third decade passed before another contribution appeared, and then 

 Cholodkovsky (1903:120) attacked the suljject from a different aspect. 

 Realizing the uncertaintj' pervading all the earlier literature — most of 

 which had appeared before the application of section-cutting to investi- 

 gation methods' — as well as the urgent need of embryological studies to 

 supplement the early work of Melnikow (1869:153), Cholodkovsky 

 not only studied mature species of Pediculus and Haeniatopinus, but 

 also many mounts and serial sections of different stages of embryos of 

 two of the species infesting man. The result led him to believe that 

 mandibles and maxillae are present in the early stages of the development 

 of the germ band but disappear entirely before the escape of the young 

 insect from the egg, and that the piercer sheath and its apparatus are 

 formed from the labimn alone. Melnikow (1869 : 153) had emphasized 

 the relationship between the Mallophaga and the Pediculidae, and 

 considered both as a family of the Rhynchota. Cholodkovsky agreed 

 with the first part of this statement, but thought the two groups should 

 rather be classed with the Orthoptera (particularly with Pseudoncuroptera) , 

 or, preferably, should be placed in a separate order by themselves, for 

 which he suggested the name Pseudorhynchota. 



