[May 2, 
^ 
^i-;.-;^^ 
%5^'i 
F[G. 15. End of body of 
Pulex canis $ ,with what appear 
to be a pair of 2-jointed cerco- 
pods (c) ; also s, the sensitive 
area (above 8), and the same 
more highly magnified ; 5, G, 7, 
8, spiracles of the correspond- 
ing segments. 
Instead of a pair of wings, 
parasitism, reduced halteres. 
"We seek in vain for all these 
analogous relations in the Diptera, 
and the assertion is therefore cor- 
rect, that all the parts of the pu- 
licid beak — with the sole exception 
perhajjs of the upper lip — as regards 
their position and use are so differ- 
ent from the homologous structures 
of Dij)tera that as to the direct 
phylogenetic relations of the two 
types of beak nothing can be said." 
"For similar conclusions as to 
the relationship of the Pulicidae 
and Diptera we may pass to the sec- 
ond group of characteristic marks ; 
viz. those of the structure of the 
thorax and its dorsal appendages. 
Instead of the universally free and 
moveable head of the Diptera, we 
have in the Pulicidae the broad 
union of the same with the pro- 
sternum. Instead of the compact 
thorax mth its scutellum so charac- 
teristic of the Pupipara, we have 
the three sej^arate thoracic seg- 
ments, without any trace of any 
dorsal mesothoracic projection, 
and, even in the extremest cases of 
nothing, absolutely nothing, as to the 
Fig. 1G. Mouth-parts of Pulex irritans. (Specimen from Paris.) 
