Dr. Karl Krapelin on the Pulicidse. 45 



placed mandibles of the Tabanidte and Culicidce, which, as is 

 proved by those Diptera which do not pierce, are only secon- 

 darily implicated in the closure of the sucking-canal, we see 

 in the PulicidjB the vertically- placed mandibles, bent in 

 towards each other laterally, appear as integral parts of that 

 tube — a different inferior closure, such as exists in the hypo- 

 pharynx throughout the whole group of the Diptera, being 

 here entirely deficient. This absence of the hypopharynx, 

 which, as is clear from what has been said, has as its conse- 

 quence a totally different importance of the mandibles, and 

 consequently a perfectly peculiar type of sucking-tube"^, 

 proves in like manner of importance as regards the discharge 

 of the salivary glands. The unpaired salivary duct in the 

 lumen of the hypopharynx is replaced in the Pulicidaa by 

 paired extremely fine half-tubes (fig. 13, s), each of which, 

 running along the inner side of a mandible, may be traced 

 from the basal part of the latter as a closed duct into the 

 interior of the head, and, further, as far as the thoracic 

 salivary gland !• 



Equally great differences in their arrangement and physio- 

 logical importance may be demonstrated by a comparison of 

 the other constituents of the proboscis of the flea with the 

 homologous organs of the Diptera. A labium unpaired 

 throughout its whole length, and at the utmost furnished at 

 its apex with one-jointed terminal lobes, occurs nowhere 

 among the Pulicidse, although something of the kind was 

 formerly ascribed to Sarcoj^sijUa. The labium of Sarcojys^Ila 

 at least presents (as fig. 8 may show) a biarticulation of the 

 " palpi," even with an indication of further segmentation, so 

 that in this point also the unity of the Pulicide group appears. 

 This difference of the segmentation of the labium in Diptera 

 and Fleas, with which a typical difference in the relative length 

 of the unpaired basal part to the paired section to be regarded 

 as palpi, goes hand in hand, can, however, hardly be so highly 

 estimated in its phylogenetic significance as the further fact 

 that the labium of the Diptera shows quite a different attach- 

 ment to the head, and so has quite a different physiological 

 value from that of the Pulicidse. In the former it generally 

 attaches itself by its gradually widening base to a more or 



* Particular attention may here be directed to the two peculiar lateral 

 lamellae of the labium, which apparent!}', by their elasticity, force the 

 upper parts of the mandibles asunder, and thus bring about a closer appo- 

 sition of their lower parts. 



t Kraft and Landois believe that they have demonstrated an opening 

 of the thoracic salivary glands into the oesophagus not far from the region 

 of the neck (see Landois, I, c. p. 18). 



