K. Jordan and N. C. Rothschild 
17 
from the edge of the segment, the presence of short spines on the inner 
surface of the hindcoxa, the division of the rod-like incrassation inside 
the midcoxa taking place near the base, and the structure of the 
modified abdominal segments. By observing these characteristics, con¬ 
fusion with other genera is easily avoided. 
The species are more numerous in Loemopsylla than in the allied 
genera, or it is perhaps safer to sajq more species have become known. 
Most of these the junior author of the present paper collected himself in 
Egypt and the Egyptian Soudan. The genus is essentially African, being 
generally found on desert mammals, one of the species ( L. cheopis ) having 
become cosmopolitan with its hosts, while three others are only known 
from Central Asia. They are essentially fleas of rodents, L. cheopis being 
especially often found on rats. As fleas leave the host when it dies, and 
take to another host, they may become the bearers of germs and hence 
the means of the spread of infectious diseases, one of the rat-fleas, 
L. cheopis, being the carrier of the plague-germ from rat to rat and 
from rat to man, and another species, L. cleopatrae, also being the 
means of the spread of disease. A special interest therefore attaches 
to the study of these insects, and we have accordingly thought it 
desirable to give here a general outline of their morphology, before 
proceeding to state the chief characteristics'by which the various species 
of Loemopsylla can be recognised. A comparison moreover of the 
morphological characters of Loemopsylla with the other fleas will show 
clearly the relationship in which this genus stands to other genera. 
As we have said above, the compactness of the body is partly due to 
a reduction in length of the thoracical segments. This reduction has 
not spread to the head, the capsule of which is large when compared with 
the thorax. The head being the bearer of the piercing and sucking 
organs which require a supply of strong muscles, there must be room in 
the caputal capsule for these organs and their retractors and extensors. 
We can therefore hardly expect to find the head reduced to any great 
extent in the fleas which have well developed piercing organs. These 
organs, consisting of the upper lip (labrum) 1 and the two mandibles, are 
slenderer and longer in Loemopsylla than in Pulex irritans, agreeing on 
the whole with those of the American non-combed eyed fleas. The 
slender type of mandible is doubtless more ancestral than the broad and 
heavily serrate type. The latter obtains in all Sarcopsyllidae and 
Spilopsyllus cuniculi, as well as in Pulex irritans, and to a less extent 
1 According to Kraepelin and Heymons, whose opinion we believe to be correct, other 
authors call the organ epipharynx. 
Parasitology i 
2 
