80 
Psyche 
[June-Sept. 
Phoridse Lonchopteridse, etc., which occupy a border-line 
position between the Brachycera and the Cyclorrhapha (be- 
ing placed among the Brachycera by some dipterists, while 
others place them in the Cyclorrhapha) . A permanent tor- 
sion of the parts apparently occurs in all true Cyclorrhapha, 
as is indicated by a displacement of the external sclerites, 
spiracles, etc., and by the looping up of the ejaculatory duct, 
etc., over the top of the hindgut (from left to right) in all 
of the Cyclorrhapha I have examined (see Figs. 17 and 19 
for illustrations of such a looping over of the parts in 
question) . 
In such Nematocera as the male Culicidse, an inversion of 
of the ninth segment (together with the proctiger, or anus- 
bearing segmental complex) occurs by rotating the parts 
(through 180 degrees) from left to right around the long 
axis of the body of the insect ; and the designation “rotation” 
should be restricted to such a transverse revolving of the 
parts around the long axis of the insect. The resulting in- 
version may be termed a rotated inversion or “transinver- 
sion” to distinguish it from the next type to be considered. 
After an inversion of this type, the anus, genitalia, etc., still 
project posteriorly along the long axis of the body. 
In many of the higher Diptera, on the other hand, an in- 
version of the ninth segment (with the proctiger) may occur 
by twisting it forward and around in a more vertical plane. 
The resulting inversion may be termed a torque inversion, or 
“retroinversion”, to distinguish it from the type of inversion 
mentioned above. After an inversion of this type, the anus, 
etc., is usually directed forward (instead of posteriorly), as 
is the case in the Syrphid Heliophilus, shown in Fig. 6, and 
in the Pyrgotid (Ortalid) Pyrgota, shown in Fig. 3. This 
type of torsion usually involves the displacement of the 
eighth sternite, which may be accompanied by the seventh 
and even the sixth, abdominal sternite as it is twisted up- 
ward. The way in which the displacement and modification 
of the parts has been brought about in the higher Diptera 
may be illustrated by a series of male Diptera shown in 
Figures 1 to 9, inclusive. 
The Bibionid Dilophus shown in Fig. 1 may be taken as 
the starting point for the series, since the condition exhibited 
by it is fairly typical of the Nematocera in general, in which 
