188 
concerned it is now unnecessary, Since the position now generally 
accorded to them with the Psocide and Termitide is generally accepted 
and its foundation on morphologic and embryologie 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. 8. Packard,* in which he sums up 
carefully the work of Melnikow and Grosse and compares their results 
with Burgess’s work on the head and mouth-parts of the Psocide, may 
be considered as final as far as regards the separation of the Mallophaga 
from the Hemiptera or their having any relationship with the Pedi- 
eulide. While the Bird-lice present decided differences from the 
Psocide 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 Lipeurus. 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 
Menoponto 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 pallidum 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 species 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 apparent ability to escape, except under particularly favorable 
opportunities. . 
In the Pediculide 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 a Hematopinus 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 Mallophagan with a Psocid, but still I think we can by such 
“Trans. Philos. Soc. for 1887, pp. 264-272. 
