THE FLEAS OF NORTH AMERICA 



least to the antennal grooves. They fuse anterodorsally, without a 

 delimiting mark of any kind, with the front. 



The front, which is so conspicuous in C tenocephalides (fig. 1) and 

 many other genera, becomes so reduced in certain families that it 

 is very inconspicuous, and in Craneopsyllus wolffhuegeli it is vestigial, 

 having been apparently overlooked in the past. As the front be- 

 comes smaller, the genae become increasingly larger. This process 

 has gone so far in the family Stephanocireidae that almost all the 

 forehead is composed of the greatly enlarged genae. 



If it were not for the fact that the front usually can be identified 

 by two of its structural features, the frontal tubercle and the dermal 

 pits, confusion frequently would exist in regard to the part it takes in 



dermal pit nr x f rorito-epLcraniaL^roove i Jerm^ p its 



ocular seta 



occipital region. 



^genal comb 



■^■^-LablaL palpi 



^--^ mandibles 



Figure 1.— Head of a flea, female of Ctenocephaiide* felis, with the different 



parts labeled. 



the composition of the head. The frontal tubercle, although sometimes 

 absent, is a well-known structure on the anterior margin of the front. 

 Usually it is sharply angulate at its apex and is situated in a small 

 notch, the frontal notch. The dermal pits are small paired pits (fig. 1) 

 which usually are located near the anterior margin of the front. The 

 maximum number of pairs on the front is three, as in such genera as 

 HoplopsyUtis, Arte n ophthalmia, and Stemopsylla. In NeopsyUa, 

 Ctt nophtkalmus, and many other genera there are two pairs of dermal 

 pits on the front. In CraneopsyUa only a single pair persists. The 

 presence of any of these pits always identifies the front. 



When the genae become greatly enlarged at the expense of the front 

 there is a tendency for each gena to become differentiated into an 

 anterodorsal and a posteroventral part. This differentiation has pro- 



