48 Dr. Karl Kriipelin on the PulicidEe. 



tionship of the Fleas to the Hymenoptera upon the sole 

 accordance of the pupse, or to the Orthoptera upon the 

 segmentation of the thorax. The order Lepidoptera also 

 cannot agree in a single one of the more important characters 

 with the Pulicidas, and thus there remains only the group 

 Ehynchota for serious comparison. As a matter of course, 

 considering the fundamental difference of development between 

 Pulicidje and Rhynchota, we can hardly expect to find real 

 intimate relations between the two groups, at least not so 

 close as we must postulate for forms of one and the same 

 order ; nevertheless 1 think I may indicate some points of 

 view which deserve to be well considered in judging of the 

 phylogenetic connexion between Fleas and Rhynchota. 



In the first place there can be no doubt that the order 

 Rhyncliota does not even ap])roximately present a unitary 

 type in the same degree as that of the Diptera. We find 

 united in it animals with suctorial and masticating buccal 

 apparatus, with perfect, imperfect, and without metamorphosis. 

 The head is sometimes freely movable, sometimes attached by 

 a broad surface to the prothorax. The thorax, so very uni- 

 formly constructed in the Diptera, shows all possible stages 

 of structure, from the enormous development of the sepa- 

 rated prothorax in Scutata and Membracina, to the compact 

 thorax sliowing scarcely an indication of segmentation of the 

 Pediculina, or tliat of many Mallophaga more or less sharply 

 divided into three distinct segments ; and like the thorax 

 itself, its dorsal appendages also present no unity of type. 

 With such polymorphism of almost all organs it is easily intel- 

 ligible that we should be able to find in this Protean group ana- 

 logies for a whole series of characters of the Pulicida\ Thus the 

 segmentation and winglessness of the thorax in the Fleas may 

 be without difficulty placed side by side with the similar con- 

 ditions among the Mallophaga, which, at the same time, 

 present examples of the antcnnary pits of the head already 

 mentioned. The absence of facetted eyes in Pulicidffi agrees 

 with what occurs in Coccida^, Pediculina?, and Mallophaga, 

 the pupa enclosed in a cocoon unites them with the Coccida? ; 

 the absence of sucking-stomach and the number of the 

 Malpighian vessels and testes are even common to them and 

 to all forms of Rhynchota. 



For the reasons above given, however, we must not ascribe 

 a serious significance to all these agreements unless the 

 Rhynchotan type sought for finds expression at least in the 

 last of the cliaracters to be discussed, those of the buccal 

 apparatus, and shows near relations to the homologous organs 

 of the Fleas. According to the present state of our know- 



