No. 64J DIPTEEA OF CONNECTICUT: MORPHOLOGY 67 



termecliate stages between the pulvilliform and true setiforni types of 

 empodium. 



The pulvilli (and pulvilliform empodium) of many flies bear 

 hollow tenent hairs, or retineriae, through which a sticky exudate is 

 poured out to enable the flies to cling to smooth, vertical surfaces, or 

 to walk about "upside-down". The pads are readily released by roll- 

 ing them inward from the margins. 



Legs of an extremely long and slender type are to be found among 

 the Tipulidae, while those of a stouter type occur more frequently in 

 the higher Diptera such as the Phoridae, Hippoboscidae, etc. The 

 bases of the legs are approximated extremely closely in the m3^ceto- 

 philids, while they are widely separated in the hippoboscids, nycteri- 

 biids, and similar forms, in which the legs usually project laterally 

 very markedly. The legs are completely lost in the females of the 

 peculiar streblid Ascodvpteron and allied forms Avhich bore into the 

 skin of their hosts and assume an appendageless, sac-like condition, 

 bearing no resemblance to a typical adult insect. 



Morphology of the Abdomen and Its Appendages 



Young (1921) has discussed the basal abdominal segments of most 

 of the dipterous families, but does not include a discussion of the ter- 

 minal abdominal structures in his fine paper on the abdomen of the 

 Diptera. Hendel (1928) describes some of the abdominal structures, 

 in his general discussion of the external morphology of the Diptera, 

 and Snodgrass (1935) and Berlese (1909) discuss the structure of the 

 abdomen of the Diptera in their descriptions of the abdominal struc- 

 tures of insects in general. The abdominal sternites of the Tachinidae 

 are described by Baronoff (1930) and parts of the abdomen of various 

 Diptera are figured in such publications as those of Seguy (1935) and 

 other general works on the Diptera: but no extensive discussion of 

 the entire abdominal region of the Diptera has as yet been published, 

 and much remains to be done in this promising field of research. Fig- 

 ures of the abdominal structures of individual Diptera will be found 

 in the publications of Hewitt (1914) on Musca, Parker (1914) on 

 Sarcophaga^ Worthley (1924) on Tnchopoda^ Seamans (1920) on 

 Anthomyia, Kuencker d'Herculais (1875-1881) on Volucella, Bromley 

 (1926) on Tabanus, Tokunaga (1930 and 1932) on Limonia and Pon- 

 tomyia, Williams (1933) on ProtopJaso., and Rees and Ferris (1939) 

 on Tipula. 



The terminal abdominal structures of the females of several 



I types of nematocerous Diptera are discussed by Gerrj^ (1932), and 

 the parts of the abdomen of the female of one or two types of Diptera 



I are figured by Boerner (1903), Berlese (1909), and Hendel (1928). 

 Discussions of the parts of the female in individual Diptera are to be 

 found in the papers of Mote (1929) on Hypoderma^ Dampf (1933) 

 on Anastrephu, Dean (1935) on Rhagoletis, Huckett (1921) on the 

 Anthomyidae, Dinulescu (1930) on Stomoxys, Patton (1934) on Glos- 

 sinu; Christophers (1923), Davis (1926), and Macfie and Ingram 

 (1922) on female mosquitoes, Metcalfe (1933) on Dasyneura, Sinton 



