32 
The Non-Combeci Eyed Siphonaptera 
Now, the study of Siphonaptera is still in its infancy. We know 
next to nothing of the geographical variation of these insects; the 
study of that question has to be postponed till a sufficiently large 
amount of material from many countries is at disposal from which the 
geographical distribution of the various forms of Siphonaptera can be 
ascertained. That there is geographical variation also in Siphonaptera 
is proved to us by several species. It is, however, decidedly best to treat 
all forms which are constantly different as being specifically distinct, 
until more of the variation of the Siphonaptera is known. 
The legs of Loemopsylla agree on the whole with those of Pulex, 
Pariodontis and Ctenocephalus, differing essentially from the legs of the 
American non-combed eyed Pulicidae both in the internal rod of the mid- 
and hindcoxa dividing nearer the base of the coxa, and in the hindcoxa 
bearing a row of teeth on the inner surface. There is considerable 
variation in the details of the shape and in the amount of bristles of the 
legs within the genus Loemopsylla, a number of species being easily 
distinguished by the legs alone. The forking of the internal rod of the 
midcoxa near the base instead of in the centre of the coxa appears to 
us a character of considerable taxonomic value, being apparently a 
specialization obtaining only in some Old World genera. 
As a rule the hind-edge of the mid- and hindcoxae of Loemopsylla is 
more or less excised before the apex, but there are also species in which 
this edge gradually slopes away. The coxae, for instance, in cheopis, 
nuhicus, pyramidis, etc. have a distinct sinus, while in isidis, creusae, etc. 
the sinus is wanting and the hindcoxa of these species is pear-shaped 
(PI. II, figs. 14-—-16). The sinus in gerbilli, mycerini, erilli, etc. is very 
shallow, the hind angle being completely l’ounded off. The number of 
spines in the comb of the hindcoxa is not the same in the various species 
of Loemopsylla, some species possessing only a few teeth, 4 or 5, while 
others have as many as 14 ( pyramidis, for instance), but the number 
of teeth varies considerably within the species. The coxal comb is only 
found in some Old World genera of Siphonaptera and some Nearctic 
forms, but not in any Neotropic fleas. The femora present likewise some 
specific differences. The most notable distinction is that found in the 
hindfemur (PI. II, figs. 6 and 7). This femur is flattened or grooved 
longitudinally on the ventral side, the edges of the flattened area con¬ 
verging anteriorly, and meeting at the point, where the ventral surface 
of the femur bears a distinct tooth-like projection. This obtains in six 
species ( pyramidis , cheopis, nubicus, cleopatrae, pallidas and eridos). In 
the other species the femur is simply rounded, the tooth being also less 
