184 Annals Entomological Society of America  [Vol. XIV, 
THE POSTABDOMEN: URITES SIX OR SEVEN TO ELEVEN. 
Previous writers appear to have completely misinterpreted the 
condition of the postabdominal segments in these males. Berlese, in 
particular, has, for some reason that I cannot understand, in his Gli 
Insetti (1, Fig. 395, A, B, p. 327) mistaken the tergites of the post- 
abdomen for the sternites and vice versa. 
The only reasons I can see for this are (a) the superficial resemblance 
of the prominent sclerites in this region to tergites of the preabdomen 
and (b) their similarity in position to the style-bearing, tenth, tergite (?’). 
The position of the appendages (styles) of this tenth urite appear to 
prove that the heavily chitinized convex sclerite marked Terg. X, 
(Figs. D, L, N, Plate IX) is the tergite; and by analogy one might 
easily assume that the preceding sclerites of similar appearance (Urite 
IX, Stern. VIII, Stern. VII, Figs D, L, N, Plate IX) are the preceding 
tergites. This Berlese appears to have done. Such assumption would 
presuppose a most remarkable twisting of the abdomen on its long axis 
between preabdomen and postabdomen. Berlese assumes that this 
twisting has been counter-clockwise, so that the mid-dorsal line of the 
sclerites that he calls lergites seven and eight, lies at the left side. As 
a matter of fact, as I shall show, the flexure has been in the opposite 
direction (clockwise); and what Berlese calls tergites seven and eight 
are sternites, while his sternites seven, eight and nine are the tergites, 
not of seven, eight and nine, but of six, seven and eight. 
The evidence for this is perfectly conclusive. The most important 
landmarks for determining homologies in this region are the spiracles 
and the longitudinal tracheal trunks. In fact, in certain species one 
can follow the lateral conjunctivee between the preabdominal and post- 
abdominal segments; and it is perfectly evident that the sclerite marked 
Stern. VI (Fig. N, Plate [X) is homologous with that marked Stern. V, 
and so with those marked Stern. VII and Stern VIII. Likewise in 
Figure M, the sclerites marked Terg. VI, VII and VIII are unques- 
tionably homologous with that marked Terg. V. More conclusive 
evidence is the course of the tracheal trunks which, as shown in Figures 
69A and 69B, Plate XIV, have no twisting or crossing over. By 
following the latter it is perfectly evident that no such remarkable 
flexure as that demanded by Berlese’s interpretation has taken place, 
(follow Figures 69A and 69B, Plate XIV). The left tracheal trunk 
passes directly back to the spiracles 6, 7 and 8: the right one bends to. 
the left and passes as directly as may be to the right spiracles 6, 7 and 8. 
The peculiar condition of the terminal urites (postabdomen) in this 
family will be best understood if we consider the changes that must have 
taken place in their development from the primitive condition of the 
abdomen. First, the caudal part of the abdomen must have become 
bent underneath, so that the sternites of the last few segments are in 
apposition to those immediately preceding (Figs. D, K, L, Plate IX). 
Following this, another important flexure has taken place as a result 
of which the segments after number seven are, secondly, successively 
displaced toward the right, curling about in a semicircle from left 
