ZOOLOGY, ENTOMOLOGY, AND MEDICINE 229 



The length of the pupal stage varies, but is at least two 

 weeks. The more specialized forms which inhabit thin cases 

 spin a thick cocoon. At the close of pupal life, the pupa cuts 

 its way out of the cocoon and swims, back downward, to the 

 surface, or to some solid object by which it can ascend to the 

 surface. There it splits the pupal skin and the adult emerges. 

 The wings dry almost immediately and the insect is then ready 

 for flight. 



FUNCTION OF THE EPIPHARYNX AND HYPO- 

 PHARYNX IN THE DIPTERA 



abstract 



Alvah Peterson, University of Illinois 



The epipharynx and hypopharynx of one or more species of 

 fifty-three families of the Diptera have been studied. In all 

 these forms the epipharynx is closely associated with the lab- 

 rum and these two parts comprise the labrum-epipharynx while 

 the hypopharynx is a separate piece in itself but it is associ- 

 ated with the labium in that its proximal portions join with 

 the labium. 



The structure of the labrum-epipharynx and the hypo- 

 pharynx is closely related with the function of the mouth- 

 parts as a whole. Generally speaking in Diptera with sucking 

 mouth-parts the labrum-epipharynx and the hypopharynx are 

 long and needle-like as in the Culicidae, Tabanidae and Asili- 

 dae, while in those having a licking type of proboscis as in 

 Muscidae, Sarcophagidae and the Drosophilidae the labrum- 

 epipharynx and the hypopharynx are short and blunt and only 

 form a small part of the proboscis. Many striking modifica- 

 tions occur in the structure of the labrum-epipharynx and the 

 hypopharynx, but in all the forms studied both parts are always 

 present. Possibly the greatest reduction of the hypopharynx 

 is found in the Borboridae. In Borborus equinus it is com- 

 pletely joined with the labium. 



This is an abstract of a more extensive discussion on the 

 epipharynx and hypopharynx of the Diptera, which may be 

 found in a paper entitled, "The Head-capsule and the Mouth- 

 parts of Diptera." This paper is to be published in "Illinois 

 Biological Monograph." 



