<)G CONNECTICUT GEOL. AND NAT. HIST, SURVEY [Bull. 



(4) The sternite of the seventh abdominal segment becomes hiter- 

 overted, or drawn up into the insect's left side, and its dextral 

 spiracle may become drawn down into the ventral region. Its ter- 

 gite becomes vestigial, or is obliterated, or may unite with the syn- 

 sternite. (5) The lateroverted seventh sternite tends to unite with 

 the inverted eighth sternite to form a synsternite, having the appear- 

 ance of a tergite. (6) The narrow sixtli sternite (bordering a genital 

 pouch in some cases) is frequently asymmetrically developed, and may 

 become attached to the lower sinistral border of the synsternite. The 

 sixth tergite tends to become reduced, but usually remains in place. 

 Tlie dextral spiracle may also shift down into the ventral region. 

 (7) Tlie fifth abdominal sternite may become bilobed posteriorly to 

 form a j)air of copulatory lobes or processes, and its tergite forms 

 the last "visible" tergite of the preabdomen in many Cyclorrhapha. 



The doAvnward shift of the dextral spiracles (Fig. 12, H and D) 

 and their displaced and distorted tracheae, and the looping up of the 

 ejaculatory duct from left to right over the top of the hindgut (Fig. 

 9a, A, and Fig. 14, H), should be evidence clear enough to convince 

 anyone that the obvious distortion and displacement of the sclerites 

 in Fig. 10, B, Fig. 12,1. etc.. is the result of a left to right torsion; 

 and the shift in the string of consecutive sternal plates in the lower 

 Cyclorrhapha (Fig. 12, F and Fig. 14, H, etc.) clearly indicates a 

 progressive shifting of the sternites, not the tergites, in these forms. 

 The torsion w^ould have to be in the reverse direction (i. e., from right 

 to left), in the face of all the evidence to the contrary cited above, 

 in order to shift any tergites into the position occupied by the obvious- 

 ly displaced sclerites shown in Fig. 10, B, Fig. 12, 1, Fig. 13, B and C, 

 etc., which are therefore clearly displaced sternites, not tergites. 

 Furthermore, it is the tergite, not the sternite, which tends to shrink 

 and become vestigial when both are present in the segments of this 

 region, (see Fig. 12, A and C), and it is therefore hardly probable 

 that such a huge sclerite as that labelled 8s in Fig. 14, H, or Fig. 12, 

 F, etc., for example, represents a tergite instead of a sternite, as other 

 investigators would maintain. 



The interpretations given the parts in the following description 

 ot the sclentes of male Cyclorrhapha are those suggested bv the 

 writer m a brief paper* entitled "Suggestions for a new interpreta- 

 tion ot the postabdomen in male cyclorrhaphous Diptera," published 

 m the Bulletin of the Brooklyn Entomological Society, Vol. 31, p. 

 141. for 193S, although the somewhat "revolutionarv" views there 

 proposed are not accepted by other investigators. The"^ views of other 

 writers, and the terms applied by them to' the parts in male Cyclor- 

 rhaplia have also been included in the following discussion, so that 

 tlic most acceptable interpretations and terminology may be selected 

 after examining the evidence available on the subject. 



Starting with the condition exhibited by a lower dipteran sm-h 

 as Uie^ibionid DUo-phus shoAvn in Fig. 12, G, we note that the ster- 



nSLhS fn"t'hr%'!?"\^'^'-"' -'' the terminal abdominal structures of male Diptera, 

 puuiished m the September issue of "Psyche" for 1941, Vol. 48, pp. 79-94. 



