188 



concerned it is now unnecessary, since the i^osition now generally 

 accorded to them with the Psocidse and TermitidsB is generally accepted 

 and its foundation on morphologic and embryologic data apparently so 

 well established that further effort may be devoted to details of com- 

 parison and the tracing of the development of special parts. 



The review of the subject by Dr. A. S. Packard,* in which he sums up 

 carefully the Avork of Melnikow and Grosse and compares their results 

 with Burgess's work on the head and mouth-parts of the Psocidae, may 

 be considered as final as far as regards the separation of the Mallophaga 

 from the Hemiptera or their having any rclationshii) with the Pedi- 

 culidfB. While the Bird-lice j)resent decided differences from the 

 Psocidse it does not require much effort to conceive of the transition of 

 a herbivorous or omnivorous insect like Atropos or Clothilla to a para- 

 site such as Menopon or Lii)eurus. Both Atropos and Clothilla occur 

 commonly in locations from which they may readily at times «travel 

 upon the bodies of either birds or mammals, and it would not require a 

 great change in food habit for them to feed upon the epidermal scales, 

 hairs, feathers, or tegumentary excretions of birds or mammals. With 

 this in mind, there is no difficulty in tracing the probable evolution of 

 this habit in the Mallophaga. We need not go far beyond any typical 

 Menopon to find a form approaching Atropos that fed either upon 

 animal or plant products, and which found suitable harbor and food 

 either on the bodies of animals or in the nests or burrows which they 

 occupied. Such species as, Menopon paUidum even now. point to this 

 habit, in that they occur not only on the bodies of birds, but infest 

 their perches and travel readily from these to the birds or to such ani- 

 mals as opportunity permits. From such si)ecies as these there are 

 examples in abundance showing every gradation of tenacity in adher- 

 ence to the host, many species even clinging to the feathers or hairs 

 long after the death of the host, and often themselves dying there with- 

 out any a])i)arent ability to escape, except under particularly favorable 

 opijortunities. 



In the Pediculidse it is hardly possible to find at present such un- 

 doubted evidence as to close affinity, though their Hemipterous nature 

 seems very apparent. It seems very probable that the group is one of 

 considerable antiquity, possibly having branched from the Hemiptera 

 proper well back toward the time of the origin of the Mammalia, and 

 springing from a more generalized Hemipteron than any now known. 



Comparing aHaematopinus with a typical Heteropteron and the essen- 

 tial differences are the absence of wings, the reduction of the joints of 

 the rostrum, the modifications of the tarsi, and the reduction of the 

 eyes. In these respects there is to be noted considerable agreement 

 with Acanthia; this latter, however, still possessing the jointed rostrum 

 and the usual form of tarsi. The correspondence is less striking than 

 that of a J^Iallophagan with a Psocid, but still I think we can by such 



* Trans. Pliilos. Soc. for 1887, pp. 264-272. 



