106 [May. 



blunt-ended processes project from the penis not far from its tip, one of whicli 

 is visible in tig. 6, -while in fig. 9 the corresponding process is hidden and 

 indicated by dotted lines. 



Fig. 1. Outline of last abdominal steruite of ^. tuhereulatus. c? . 

 „ 2. „ „ „ „ „ E. strl(/atus. c?- 



„ 3. Left hind leg of E. tuberculatus. S • 

 „ 4. View of fig. 5 from the right. 

 „ 5. One half of " shell " of U. tuberculatus hjpopygium viewed from 



the inner side. 

 „ 6. Profile of aedeagus (penis and its appendages) of E. tuberculatus. 

 „ 7, 8, and 9. Corresponding figs, of male genital parts of E. striyatus. 



Figs. 1-3 X by about 28. Figs. 4-9 x by about 45. 



Newmarket. 



April 1920. 



RECENT RESEARCH ON THE HEAD AND MOUTH-PARTS 

 OF DIPTERA. 



BY A. D. IMMS, M.A., D.SC. 



The following remarks are the outcome of a perusal of a recent 

 paper by Peterson,* which may he commended Avithout hesitation as 

 being worthy of the attention of all students of Diptera. Its particular 

 value lies in its great wealtli of clear illustrations (606 in number) and 

 the extremely wide range of species (pertaining to 53 families) which 

 have been resorted to for examination. Peterson's Avork represents the 

 most recent attempt to unravel the complexities of the dipterous head 

 and mouth-parts by means of comparative morphology, and is a valuable 

 contribution to that method of appi'oaeliing the subject. Finality, how- 

 ever, cannot be arrived at by this method alone. Palaeontology has, so 

 far, aided us but little, and the remaining court of apj^eal is consequently 

 that of embryology and post-embryonic development. Unfortunately, 

 students of insect-development, in the widest sense of the term, are 

 extremely few, the methods of technique are often difficult, and it is a 

 line of research which demands the trained skill of the experienced 

 hiologist. The greatest need at the present time is a prolonged investi- 

 gation of the changes undergone in the dipterous head during pupal life. 



It is to be observed that Peterson reverts to the generally accepted 

 opinion that the palpi of Diptera are maxillary organs, and rejects the 

 conclusions of Wesche that they belong to the labium. The vestigial 



* Peterson, A., 1916, "The Head-cap8ule and Mouth-part sof Diptera," Illinois Biological 

 Monographs, vol. ill, no. 2, 113 pp., 25 pis- 



