52 Dr. Karl Krapelin on the Pulicidge. 



also came to full development and importance, can hardly 

 be regarded as a serious obstacle to the homology here 

 attempted. 



The preceding indications will suffice to prove that in fact, 

 without any great violence to the data given, a certain parallel 

 may be drawn between the buccal organs of the Fleas and 

 those of the higher Rhynchota, and that this comparison is at 

 least far easier to carry out than that between the Pulicidge 

 and the Diptera. If we bring the other agreements and diffe- 

 rences of the three groups in question into the account, the 

 result must be a phylogenetic alliance, although a distant one, 

 of the Fleas with the Rhynchota rather than with the Diptera. 

 But I repeat that the demonstrated relations certainly by no 

 means justify a union of the two groups. The only possi- 

 bility that presents itself is therefore to place the Pulicidse as 

 an equivalent order Siphonaptera "^ side by side with the two 

 most nearly allied orders. 



The entire series of insects with suctorial mouth-organs 

 would consequently have to be divided in the first place into 

 two groups, one of which (Hymenoptera, Lepidoptera) is 

 characterized by having the lower parts of the mouth, maxillse, 

 and labium employed in the formation of a sucking-apparatus, 

 while in the other, on the contrary, it is almost exclusively 

 the upper parts (labrum and mandibles) that are implicated 

 in the formation of the true food-canal. This latter group 

 would include the three orders Diptera, Siphonaptera, and 

 Rhynchota, which 1 may, in conclusion, briefly characterize 

 as follows : — 



1. Diptera. Insects with perfect metamorphosis. Head 

 free, with facetted eyes. Sucking-tube formed by a dorsal 

 and a venti'al half-channel (labrum and hypopharynx), more 

 or less enclosed throughout its length by the labium, which is 

 bent up like a sheath and furnished with uniarticulate apical 

 palpi. Mandibles deficient or styletiform, pushing in between 

 the labrum and hypopharynx. Maxillge, when present, with 

 palpi. Salivary efferent duct an unpaired closed canal in the 

 interior of the hypopharynx. A " sucking-stomach." Tho- 

 racic segments amalgamated, usually with a pair of wings and 

 a pair of halteres. 



2. Siphonaptera. Insects with perfect metamorphosis. 

 Head attached to the thorax by a wide surface, without 

 facetted eyes. Buccal organs suctorial. Sucking-tube formed 



* As the name " Aphaniptera " is inadmissible for reasons already 

 given, and that adopted by Taschenberg-, " Suctoria," has already been 

 employed twice, for a group of Oirripedes and for the Acinetse, I think 

 it best to fall back upon Latreille's name " Siphonaptera." 



