REVISION OF THE SARCOPSYLLIDAE 
21 
The row of short hairs so often found along the antennal groove in many of the 
Pulicidae, especially in the $$, is absent in the Sarcopsyllids. 
The majority of the Pulicidae have the genal edge of the trons armed with a 
comb of long teeth (genal comb), which the specimens, judging from live individuals 
put in cotton wool, apparently use in moving through the fur of the host. This 
comb is absent from the greater number of species of the genus Pulex, for instance, 
from P. pallidas, cleopatrae, boh/si, etc., while in Pulex irritans the comb is usually 
represented by one or two very small teeth only, which are often absent. In two of 
the species of Pulicidae known to us the comb appears to be replaced functionally, not 
morphologically, by one large tooth-like projection, the prolongation of the post-oral 
angle formed by the oral and genal edges. This post-oral process is found in 
Lycopsylla novus and in Pulex riggenbachi. In Ctenopbtbalmus wenmanni there are two 
genal spines above a small post-oral process. All the Sarcopsyllidae without exception 
possess a large triangular post-oral process, which is more or less curved backwards 
(PI. I, Fig. 1-5). This hook resembles the conical projection into which the 
prosternite is prolonged. A similar projection is met with in the of Hectopsylla 
coniger and broscus on the episternum of the metathorax, while the metathoracic 
epimerum bears dorsally also a similar, but curved, process (PI. I, big. 5). These 
processes, as well as a lateral lobe of the hind margin of the occiput of the g of 
Echidnophaga gallinaceus, have all doubtless the function of helping to prevent the 
specimen from slipping back when pushing itself through the fur or feathers of the 
host. The two lobes which are placed on each side of the head at the frontal oral 
angle in all Ceratopsyllidae (bat-fleas) serve presumably the same purpose, but are not 
homologous to the post-oral lobe of the Sarcopsyllidae, and of the few Pulicidae 
mentioned above. It is significant that similar processes are found on the thoracic 
pleurae in MalacopsyHa, the of which genus fix themselves permanently (or at 
least for a longer period) on their host, resembling in this respect the of 
Sarcopsyllidae. In the likewise stationary Vermipsylla alacurt there are no such 
processes. 
The peculiarities in the structure of the caputal capsule cannot be well discussed 
without reference to one of the most conspicuous features in the organization of the 
Sarcopsyllidae^ the enormous reduction of the thoracic tergites. This reduction, 
which we find already indicated to a small extent among the Pulicidae in Pulex irritans 
and leporis, and the members of the genus MalacopsyHa, but not in the genera 
Vermipsylla and Chaetopsylla, is not present to the same degree in all Sarcopsyllids, the 
tergites being much longer for instance in Echidnophaga bradyta than in the species of 
the genus Dermatopbilus. As the reduction of the tergites is not accompanied by a 
correspondingly marked decrease of the sternites, the reduction must naturally have 
an effect on the shape of the head. The Sarcopsyllidae follow in this respect two 
distinct lines of development, which we must consider separately. The stages of 
