46 Dr. Karl Krapelin on the PulicidEe. 



less developed cephalic cone, with the upper lateral parts of 

 which it is connected, and so is enabled from the base onwards 

 to form that sheath of the delicate piercing apparatus (the 

 two pairs of jaws as well as the labrum) which often arches 

 together above so as to constitute almost a closed canal. In 

 the Fleas, on the contrary, there is no such union of the 

 labium with the lateral or upper parts of the head ; it simply 

 articulates with a firm brown chitinous piece (fig. 9, cJi) 

 in the median line of the lower surface of the head, and this 

 union, as is well known, is frequently so loose that it is 

 difficult to obtain Sarcopsyllce^ for example, with the labium 

 preserved *. Hence, in its basal part, it does not form the 

 sheath for the piercing-apparatus, but shows only a compara- 

 tively shallow groove (fig. 15), which only in the ante- 

 rior section of the proboscis, when the stem of the labium has 

 become cleft into the paired palpi, becomes developed, at least 

 in Pulcoc^ into two flaps, embracing the piercing-organ at the 

 sides (fig. 10, Ip). But to make up for the deficient protec- 

 tion of the basal part of the sucking-tube (and in this we have 

 a fundamental deviation from the type of the Diptera) the 

 maxillaj hava come in, originating as two broad plates from 

 the whole length of the side of the head, and taking here, not 

 only the constituents of the piercing-apparatus, but also the 

 base of the labium, under their protection, as shown by fig. 15 

 in Pulex. 



We seek in vain for analogies to all these characters among 

 the Diptera, and we may therefore be justified in asserting 

 that all the parts of the Pulicide proboscis (with the sole 

 exception perhaps of the labrum) differ so much in position 

 and employment from the homologous parts in the Diptera, 

 that we cannot well speak of direct phylogenetic relations 

 between the two types of proboscis. 



We arrive at precisely similar conclusions as to the rela- 

 tionship of the Pulicidaj and Diptera when we take into 

 consideration the second group of characters peculiar to the 

 Diptera, Avhich appear in tlie structure of the thorax and its 

 dorsal ojypendages. Instead of the always freely movable 

 head of the Diptera, we find a broad union of it with the pro- 

 thorax in the Pulicida3 j instead of the compact thorax with 

 its scutellum, Avhich is so characteristic even of the wingless 

 Pupipara, we have three sharply separated thoracic segments, 

 without a trace of any such dorsal mesothoracic process ; and 

 instead of the pair of wings and the halteres, the latter of 

 which are aborted only in the most extreme cases of parasitism, 



* Even in recent handbooks we may find the statement that the 

 labium of Sarcopsylla is indistinct. 



