1887.] ^^* 1 Packard. 



and sliort, of the masticatory type in the Mallophaga, while in the Pedi- 

 culus they remain large and long (Meluikow, Fig. 371) and of the size and 

 shape of the mandibles ; the second maxilhc in Pediculusare, in this stage, 

 as large as iu the first maxillae, -while in the ]\Iallophaga they become minute. 

 After the stage indicated by Melnikow's Fig. 37 (Pediculus) and Figs. 32, 

 33 and 34 {Trichodectes canis) the ordmal differences become more 

 marked. 



Among the Pscudoneuroptera of Erichson, a group which is so unnatu- 

 ral that it will have to be abandoned, we have after the elimination of the 

 Odonata and the Plectoptera or Ephemeridaj, the families of Perlida;, 

 Psocidiv, EmbidaJ, and Termitidoe, which we have associated together in 

 the order Plutyptera. It is to the wingless Psocidae that the Mallophaga 

 appear to bear the closest resemblance. If we compare certain 3Iallo- 

 phaga, especially those with a small prolhorax, such as Goniocotes, Doco- 

 phorus, etc., with the wingless Atropos, or the wingless young of Psocus, 

 there is a general similarity to the latter in the small thorax, the large 

 oval abdomen and the large head, with the small eyes. But these resem- 

 blances are superficial. But, however, with the aid of Grosse's figures 

 of the mouth-parts of the Mallophaga and Mr. E. Burgess' excellent fig- 

 ures of the mouth-parts of the Psocidai*, three of which we reproduce, 

 we find an unexpected homology, which shows that the Mallophaga are, 

 so to speak, degraded Psocida;. 



One characteristic of the Mallophaga, in general, is the greatly enlarged 

 front or clypeal region of the head, which is vaulted and conceals from 

 above the mouth-parts, and sometimes even the antennae, with the occa- 

 sional exception of the labial palpi. In the bird-lice, the lower, rounded 

 edge of this circular clypeal region is applied to the surface on which the 

 animal rests, as seen in Figs. 1 and 5, the labium and mouth-parts not 

 being seen from above, except iu some genera where the maxillary palpi 

 project lateral lj\ 



In the PsocidiE the position of the head is vertical, as seen iu Fig. 10, 

 and the labrum is not covered by the clypeus ; but the ]\Iallophaga are 

 unlike these and other insects in having the labrum covered by the cly- 

 peus. 



In the shape of the mandibles the Mallophaga closely resemble the 

 Psocidae, at least as much so as perhaps any oilier of the biting insects. 



Mr. Burgess has figured and described the first maxillae of Psocus (Figs. 

 10 and 11) and Atropos (Fig. 12). The cardo and stipesare rudimentary ; the 

 latter bearlngbesides the four-jointed palpus a thick fleshy lobe homologous 

 with the galea or outer maxillary lobe of other biting, ametabolous insects. 

 He also describes at length the peculiar " fork," which has no homologue 

 in the Mallophaga any more than other insects, Mr. Burgess inclining to 

 the view that this is an independent organ. It is to be noticed that, with 

 the exception of the palpi, the maxillae of the Psocidae are much atrophied. 



* The Anatomy of the Ilesid, and the Structure of the Maxilla in the Psocidte. By 

 Edward Burgess. Proc. Boston Soc. Nat. Hist., xix, 291-29G, 1878. 



