20 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
The frons bears only two bristles of any length, the one standing before the eye and 
the other near the insertion of the maxillary palpus, a small hair being placed between 
or above them. These bristles are constant in number in the genera Echidnophaga and 
Hectopsylla, but the eye-bristle is placed a little higher in the latter genus than in the 
former. In the two species of Dermatophilus these bristles are much reduced or even 
absent. The position of the eye-bristle in front of the eye is a generalized character 
present in the majority of fleas. Only a few of the true Pu/icidae, namely irritans* 
and its close allies, have the eye-bristle beneath the eye. The Sarcopsyllids having 
kept the original position of the bristle it is beyond doubt that they are not derived 
from a form identical with the present day irritans. The frontal bristles are most 
developed in E. gallinaceus. 
The occiput normally bears three rows of bristles in the Siphonaptera. The first 
row is placed behind the base of the antennal groove (where the antenna is inserted), 
the second, or median, row in the centre of the side, and the third or subapical, row 
near the hinder edge ot the head. There are frequently intermediate bristles as well, 
more or less arranged in rows. The most ventral bristle of the subapical row is every- 
where the longest occipital bristle. Among the Sarcopsyllidae all the three normal 
rows are represented in the genus Hectopsylla only, the other genera presenting all 
grades of reduction in the number of the bristles down to almost total disappearance. 
The f of Hectopsylla psittaci exhibits the largest number of occipital bristles in 
the most normal position. In this ? we find two bristles near the base of the antennal 
groove, two or three in the middle of the side, and three or four near the hinder edge. 
The $ of this species has practically the same number of bristles, but a curious 
shifting of the last row may be observed. The most ventral bristle of this row 
retains its normal position, but the other subapical bristles, or at least some of them, 
are more or less moved forward so as to form a single row with the median bristles. 
The subapical row, therefore, appears to consist in this $ usually of one bristle only, 
mostly accompanied by a small hair, there being occasionally an additional long bristle 
above the antennal groove, making four in all ot such supra-antennal bristles. The 
bristles of the occiput are similarly placed in both sexes of Hectopsylla coniger, and in 
the of Hectopsylla broscus and pukx, of which the ff are not known. From an 
examination of these last three species alone it might be erroneously concluded that 
the subapical row of bristles was practically absent. None of the other Sarcopsyllidae 
have three long bristles immediately above the antennal groove, the bristles of the 
anterior row being either absent or represented by minute hairs. The median bristle 
and the subapical one remain relatively long in Echidnophaga gallinaceus, murina y 
and a new species, while only the subapical one is well developed in the other species 
of Echidnophaga. In Dermatophilus this last bristle is also small, there being in this 
genus, moreover, only a few tiny hairs belonging to the median and subapical rows. 
* A list of the Siphonaptera referred to in this introduction will be found at the end of the introduction. 
