REPORT OF THE STATE ENTOMOLOGIST I907 250 
tends posteriorly under the lobes y and appears at the point 
marked w. This structure lies in Zygoptera in a position ex- 
actly corresponding, so far as the penis is concerned, to some of 
the sheaths of Anisoptera and evidently it has a similar func- 
a b 
Fig. 25 
tion. It is chitinized above and lies over and anterior to the 
reflexed penis. The posterior lobes of the anterior lamina no 
doubt function like the first pair of hamules in Anisoptera. 
& shows a pit, a small hole, found in this segment as well as 
in segments 1 and 32 in a great many instances among both 
suborders. 
Figure 25 a, b, d and e shows also some of the different lobes of 
the anterior lamina common to the Zygoptera. (e) is from Argia, 
(d) from Nehallennia, (b) from Lestes and (a) from Anisopleura. 
Returning now to the parts developed from the rear of 
the sternum of the 2d abdominal segment (the sternellum), 
let us further consider the development of parts immediately 
adjacent to the penis, the protecting sheath and the hamules. 
The very remarkable structure of the penis itself has been de- 
tailed and figured by Hagen in Monographie des Gomphines, 
and elsewhere. The tips of the hamules have been figured for 
many forms by many authors, but the forms and relations as- 
sumed by the penis sheath have scarcely been noticed hitherto. 
In figures 26 and 27 are shown two series of forms of the penis 
sheath, illustrating the comparative development of two differ- 
ent types of sheaths found among the Anisoptera. 
igure 26) p iS one of the simplest sheaths found: lit is 
a flat, translucent sheath, thin, excepting the edges, lying in 
a horizontal position below the penis. » shows the portion of 
