No. 64] DTPTERA OF CONNECTICUT: MORPHOLOGY 81 



so-called sternal valves, valvae inferiores, or "e<r<^-oiiides" of the 

 egg-laying apparatus (the so-called "ovipositor") whose ''tergal 

 vah'es" are formed by the cerci, ee. 



The type of egg-laying apparatus described above should be re- 

 ferred to as an oviscapt, or ovicauda, rather than an "ovipositor'', in 

 these Diptera, since its parts are not strictly homologous with those 

 of a true ovipositor of the type occurring in orthopteroid insects, in 

 which the ovipositor valves are made up of parts of the modified 

 appendages of the eighth and ninth abdominal segments. The ster- 

 nal valves, hg of the tipulid shown in Fig. 9, A, may possibly be 

 homologous with the ventral valves of a true ovipositor* (although 

 they may be merely secondarily-formed valvular processes of the 

 eighth sternite), but the cerci, ce^ which form the tergal valves of tlie 

 so-calied ovipositor in the tipulids, are never involved in the forma- 

 tion of the valves of a true ovipositor of the orthopteroid type, etc.; 

 and even in the higher Diptera, the cerci do not. as a rule, form any 

 considerable part of the egg-laying apparatus (though they may pos- 

 sibl}'^ do so in the female cyclorrhaphan shown in Fig. 9, D). 



In the female tipulids described by Snodgrass (1903), paired 

 sclerites of the eighth sternite, which may unite to form a bifid plate 

 projecting from the floor of the genital chamber, are called the "first 

 gonopophyses" by Snodgrass, who also applies this designation to the 

 anterior, or ventral valves of the true ovipositor of orthopteroid in- 

 sects. 



Snodgrass calls the processes of the ninth sternite the "second 

 gonapophyses" in female tipulids, and also applies this designation to 

 the intermediate valves of the true ovipositor of the orthopteroid 

 insects in which the intermediate (or inner) valves of the ovipositor 

 are appendages of the ninth sternite, but the exact homologies of these 

 structures in the Diptera have not been definitely determined. The 

 parts of the ninth sternite, 9.s, of the tipulid shown in Fig. 9, A, are 

 greatly modified, but in the present state of our knowledge of these 

 structures, it is impossible to interpret them definitely in terms of the 

 parts of orthopteroid insects. The location of the gonopore of the 

 female tipulid shown in Fig. 9, A, is indicated by the label gpo. 



Snodgrass (1903) finds the representatives of the paraprocts, or 

 parapodial plates of the eleventh segment of orthopteroid insects, in 

 the tipulids described by him; and the bipartite plate below the anal 

 opening, ao of the tipulid shown in Fig. 9, A, may bear some relation 

 to the paraprocts. although this has not been definitely determined. 

 Traces of the dividing line between the tenth tergite and the eleventh 

 segment (represented by the plates, etc., at the base of the cerci. ce) 

 are retained in the tipulid shown in Fig. 9, A, and this type of female 

 dipteran furnishes an excellent starting point for tracing the gradual 

 fusion of the segments behind the ninth, and their ultimate adhesion 

 to the ninth segment, in the higher Diptera. 



The cerci of the tipulids are occasionally of the nature of blunt 



* In some tipulids, processes of the ninth sternite may represent the dorsal valves 

 of a true ovipositor. 



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