112 CONNECTICUT GEOL. AND NAT. HIST. SURVEY fBuU. 



The non-segmental. anus-bearing telson. the cerciis-bearing- elev- 

 enth abdominal segment, and the tenth segment tend to unite to 

 form a terminal, anus-bearing segmental complex in tlie lower insects, 

 and there is every reason to pippose that the so-called "anal segment" 

 of the Diptera was formed in the same way, unless the eleventh seg- 

 ment (or the tenth) merely dropped out, instead of uniting with the 

 others, wliich is not very probable. If the appendages labelled ce 

 in Fi'j. 13. El. etc., are really the cerci, or appendages of the eleventh 

 segment, then the cercus-bearing eleventh segment must have entered 

 into the composition of the ''anal segment" in the Diptera, altliough 

 Edwards (11)20) and others who refer to the ''anal segment" in the 

 Diptei-a, usually interpret it as the tenth segment alone, even when 

 they accept the view that the appendages it bears are true cerci ! 



It is inadvisable to refer to the proctiger, pg)\ of Fig. 13, E, etc., 

 as the ''anal segment" in the Diptera, since it is not a single segment, 

 but is a[)i)arently a segmental complex bearing the anal opening; 

 and the tcIson, or true anus-bearing terminal ]'egion, is not a segment, 

 but is meiely a terminal region which does not contain caeloni sacs in 

 the embryonic stages of arthropods in general (i. e., it corresponds to 

 the telscm of the Crustacea, etc.). Furthermore, the designation "anal 

 segments"* is sometimes applied to the ninth segment and the preced- 

 ing segmental complex in male sarcophagids, etc., and in such cases it 

 would be confusing to refer to the anus-bearing region as the "anal 

 segment", so that it is preferable to refer to the anus-bearing region, 

 j)(ji\ as the proctiger in the higher Diptera, as is done in the lower 

 forms. 



The cerci, ce, of Fig. 13, D, E. and F, or Fig. 7, K, etc., of the males 

 of the higlier Diptera, are homologous with the structures called cerci 

 in male mosquitoes; and Christophers (1923) has shown that at least 

 the distal portions of these structures of the males correspond to the 

 cerci of female mosciuitoes and other Nematocera. These in turn 

 appear to be homologous with the structures which most entomologists 

 agree are true cerci in female Mecoptera. It therefore seems probable 

 liuit at least the distal portions of the structures labelled ce in the 

 ligui-es of the males of the higher Diptera are formed by the cerci, 

 although the parapodial plates (or paraprocts) may possibly contrib- 

 ute to the formation of the basal regions of these structures, and in 

 fact Wesche (1906) suggests that these processes of the higher Diptera 

 are homologous with the parapodial plates (paraprocts) of the roach 

 PerijAmwta, and Cole (1927) also homologizes them with the para- 

 ])rocts of lower insects. In the present discussion, however, these 

 structures will l)e referred to simply as the cerci in the males of the 

 higher Diptera. 



Berlese (1909) was the first to homologize these structures in the 

 Di])tera with the true cerci, or appendages of the eleventh segment, 

 and calls them acrocerci in male syrphids (cv? of Fig. 12, F), altliough 

 he calls the same structures the "mesocerci" in the°male housefly {ce 

 of Iig. 13, F) and considers that they are appendages of the tenth 

 segment m the latter insect. Awati (1915), Metcalf (1921), Hendel 



