1887.1 ^«1 [Packard. 



sect has some external similarity with those parasites, and because I en- 

 tertained the idea, that the internal structure of tiie same might oflc'r 

 some points which would be of value in throwing light on the natural 

 affinity of the insect parasites, at least of the biting species." The fol- 

 lowing comparisons are taken from Nitzsch's memoir : — 



"The digestive canal oi A. pulsatorius differs from that of the Mallo- 

 phaga only in the crop and the constantly present upper flap or diverticu- 

 lum of the stomach. There are four simple, unbranched ]\Ialphigian 

 tubes both in A. pulsatorius and in the Mallophaga. Of ovarian tubes 

 there are five pairs in A. pulsatorius, and jn Mallophaga from three {Lio- 

 theidce) to five pairs (Philopieridce)." After describing the ovaries and 

 oviduct, he goes on to say : "Herein appears an unexpected similarity be- 

 tween the Psocidae and the animal insect parasites, for the entire structure 

 of their uterus and the number of their ovarian tubes, also the shape of 

 the egg itself, is like that which had already been described by Swammer- 

 dam in the louse, and by myself in the genera Philopterus and Tricho- 

 dectes. In Liotheum and Gyropas, however, the number of ovarian tubes 

 is somewhat smaller." 



In the nature of their food and their manner of taking it there is a close 

 resemblance between the Psocida^ and Mallophaga. 



As is well known, the Psocidae occur on the trunks of trees, fences, old 

 walls, etc., and feed on decaying vegetable matter. " Atropos, as is well 

 known, lives on the paste in old books and boxes, as well as the speci- 

 mens of entomological cabinets" (Burgess). While the food-habits of 

 the Mallophaga are not fully known, Nltzsch stated that they eat the epi- 

 dermal products of birds and mammals, and sometimes blood. Grosse 

 found that blood is rarelj'^ taken, and only in cases where the hosts (birds) 

 are so injured or diseased as to have blood among their plumage. Leuc- 

 kart arrived at the same result as to Trichodectes canis of the dog. In 

 Li^cmobothrium, Grosse found the intestine filled with the limbs of its own 

 kind, as if it ate the product of its own moulting. 



From the present state of our knowledge then, it seems reasonable to 

 infer that the Mallophaga are nearest allied to the Psocidae, and are de- 

 graded members of the order to which the Psocidae belong. 



It now remains to determine the exact relations of the Mallophaga to 

 the order containing the families of Termitidae, Embida?, Psocidae, etc., 

 and here we are confronted with the difficulty of limiting the order con- 

 taining these families, which were with other groups placed in the order 

 of Pseudoneuroptera by Erichson. In my essay on "The Systematic 

 Position of the Ortlioptera in relation to other orders of Insects,"* I 

 retained, though under protest, this order; at the same time stating, "It 

 is difficult, if not impossible, to satisfactorily characterize by a sharp-cut 

 definition this very elastic order. As regards the thorax, there is no uni- 

 formity in the structure that we have been able to discover, nor is there in 



* Third Report U. S. Entomological Commission, 1883, pp. 286-345. 



