44 Dr. Karl Krapelin on the Pulicidge. 



pharjnx (Gerstfeldt), as the epipliarjnx (Karsten), and lastly, 

 as already mentioned, as the '' tongue" (Savigny, Taschen- 

 berg), and therefore all serious homologizing must have been 

 prevented, the more, as even the real components of the suck- 

 ing-tube were not made out with certainty. 



In figs. 10 and 13 I give two transverse sections through 

 the anterior part of the Pulicid proboscis. Fig. 10 represents 

 a section from Palex irntans ; fig. 13 a simihir section, but 

 nearer the base of the proboscis, from Sarcopsylla penetrans'^ . 

 The sections show at once that the structure of the sucking- 

 tube in tlie two most distant groups of the Pulicidse is quite 

 accordant. In both cases it is the mandibles hnd), which, in 

 conjunction with the " unpaired piercer," form tlie true food- 

 canal ; embracing the latter above and laterally, they join 

 firmly together in the median line below. A glance of com- 

 parison at figs. 1-3 shows that this " unpaired piercer " is 

 hollowed into a groove on the underside exactly in the same 

 way as the lahrum of the Diptera, and that to begin with 

 there is no hypopharynx, but at the utmost perhaps an 

 epipharynx. But if we trace the further course of this struc- 

 ture by the aid of longitudinal and transverse sections it is 

 easily seen that its upper covering immediately after its en- 

 trance into the capsule of the head is in chitinous union with 

 the upper margin of the arch of the head, while the inferior 

 plate, i. e. the one which immediately forms half the sucking- 

 channel, passes continuously into the chitinous covering-wall 

 of the pharynx. Consequently we find in the organ in ques- 

 tion precisely the same conditions as in the labrum of the 

 Diptera, and there is no doubt at all that we have to do here 

 with a true labrum. A connexion of this with the labium 

 by means of a strongly chitinized, brown uniting piece, as 

 asserted by Duges (/. c. p. 150), really has no existence at allf, 

 and this removes the last possibility of regarding this struc- 

 ture as a " tongue," i. e. as an extension or appendage of the 

 labium. 



The interpretation of the " unpaired piercer," as labrum, 

 being thus established beyond a doubt, the comparison of the 

 proboscis of the flea with that of the Diptera can present no 

 further difficulties. The employment of the labrum {Ir) as the 

 unpaired covering lamella of the food-canal is apparently the 

 same in both groups. But it is otherwise with the other 

 components of the sucking-tube. In place of the horizontally- 



* The material was kindly sent to me from Assumption by my honoured 

 colleague Dr. H. Toppen. 



t This chitinous piece rather forms the lever for moving the mandible, 

 a.s will be shown elsewhere. 



