Packard.] 326 ^^''^ ^• 
there are maggot-like larvae in groups standing far apart from tlie 
dipterous type, among llymenoptera and Coleoptera, and tliere- 
fore tliis should probably not be decisive in settling the question 
as to the relations of the fleas to the Dii)tera." 
Comparison of the pupa of Jleas with that of Diptera. — Kraepelin 
states that the pupa of the flea with its limbs entirely free differs 
so much from the fundamental type of non-coarctate mummy 
pupae that one author (Dugtis) has already attempted on these 
grounds to construct a relationship of the fleas with the Hyme- 
noptei-a. 
The absence of any rudiments of wings in the pupa of the flea 
is characteristic of this order, those of Diptera being in many 
cases provided with the rudiments of both j^airs, much as in 
lepidojsterous pupae. 
This subject needs working over, for the rudiments may yet 
be found ; and the imaginal discs should be sought for in the 
larva. Perhaps the result of such studies will throw some 
additional light on the relations of the Siphonaptera to the 
Diptera. 
COMPAKISON OF THP) ImaGO StAGE OF SiPHONAPTERA WITH THAT 
OF Diptera. 
In comparing the structure of the adult Siphonaptera with that 
of the Diptera we shall have to rely on the work of Kraepelin, 
who justly claims that a study of the mouth-parts of the two 
groups, as well as that of the thorax and its appendages, will alone 
enable lis to arrive at a decision of the question in dispute ; also 
on the later researches of Wagner. We will first give an abstract 
of Kraepelin's researches. While, he says, the unpaired organ 
of the mouth-parts is the labrum (he also calls it the epipharynx), 
which is the homologue of that of the Diptei-a, the same cannot 
be said of the other components of the sucking tube of the two 
groups. 
The hypopharynx, present in all Di^itera, is found also in the 
Pulicidae. 
There are also great differences in the structure and physio- 
logical uses of the flea's beak, as compared with tliat of the fly. 
A labium extending, as in Diptera, unpaired the whole length, 
and provided at the end with a one-jointed terminal lip (endlippen) 
