The Mouth-parts of th Nemocera. By V,'. We& 5 



Group 8. — All parts atrophied. 

 GEstridse. (Type G. equi !•".) 

 The genus Oncodes of the < '\ rtidze. 



Pulicidje— With regard to the inclusion of the Pulicidte in 

 the order Diptera, some of my preparations of P. irritans L. £ 

 show a very characteristic "chyle stomach," and a single recep- 

 taculum seminis in the abdomen, which seem very close to similar 

 organs in Diptera. On the dorsal part of the ovipositor of Pipun- 

 culus campestris Ltr. is an organ which, from its situation, and 

 from a certain superficial likeness, appears to be homologous with 

 the well-known pygidium of the flea. These are three items of 

 evidence in favour of their being retained in the classification. 



A study of the phylogeny of the Phoricke has necessitated a 

 review of the tropin of the large majority of the families, and this 

 lias led to the knowledge that in the mouth there is an additional 

 character which separates the two great divisions of Diptera, the 

 Orthorrapha and the Cyclorrapha. 



All the families with complete mouth-armature are in the 

 Orthorrapha, but in other families, when the mandibles disappear, 

 they are imbedded in the ventral side of the labium, as in Bibio 

 hortulanus L. and Tipula oleracca, or Dolichopus griseipennis Stan., 

 while in the Cyclorrapha they are imbedded on the dorsal side, as 

 in Ildophilus pendulus L., and Ccdliphora erjjthrocephala Mg. ; or, 

 To put the matter in a simpler way : In the Orthorrapha (a) when 

 the mentum is developed, a median suture or thickening of the 

 chitin is present; (b) when undeveloped, paired rods will be found 

 on the ventral side of the labium. In the Cyclorrapha the median 

 line of the mentum is not indicated by a suture. 



This character is fresh evidence that the two great divisions of 

 Diptera are natural, and makes the task of classification easier 

 (plate I. figs. 14, 15, and plate IV. figs. 59, 60). 



Group 1. — The presence in several families of an organ some- 

 what similar to the pharyngeal pump in Culex, has directed my 

 attention to that part. I borrow the nomenclature from Dr. 

 Xuttali's and Mr. Shipley's paper on Anopheles.* It consists of 

 three chitinous plates, situated in the head and forming a chamber 

 having ducts leading to the pharynx and the buccal cavity. Tin 

 plates are attached by muscles to the head walls, and when pulled 

 back by them, create a vacuum which sucks up the blood or fluid 

 through the hypopharynx, which is prevented from returning by a 

 valve in the anterior duct. It seems to be formed from the 

 pharynx, which at this point often consists of a chitinous tube. 

 Its presence in such very old families as Ptychoptera, Tipula, and 

 the Australian genus Gynoplistia shows it to be a very archaic 



* Journ. of Hygiene, i.. No. I (1901). 



