REPORT OF THE STATE ENTOMOLOGIST I907 253 



Libellulidae. h is situated between the first and second hamules. 

 It is my opinion that the first pair of hamules are developments of 

 the posterior and outer sides of the anterior lamina, while the sec- 

 ond pair are the terminations of the posterior portion of the frame- 

 work which swings around close to segment 3 in this figure. This 

 point is discussed, more fully, later. shows the penis and seminal 

 vesicle developed on segment 3. 



The next figure {d) is a sketch representing the relation of 

 parts typical for the entire suborder Zygoptera. The most 

 apparent difference between this and the two figures explained 

 above is in the location of the penis, p this being on the 

 2d segment here, and seemingly in an exactly homologous po- 

 sition to that of the sheath of Anisoptera. The supporting 

 framework is constructed on the same plan as that of Anisoptera, 

 m being the anterior portion which passes under the penis 

 and also under the lobes of the anterior lamina and n the 

 posterior portion intimately associated with the hamules h. Only 

 one pair of hamules is noted; however, associated with this fact, 

 one must notice the remarkable development of the posterior 

 portion of the anterior lamina of which the lobed portions 

 divided well back, appear like a second pair of hamules, and 

 no doubt so function, while the smaller chitinized structure 

 between the lobes of the lamina and just anterior to and over 

 the penis, formed by an infolding of the under side of the 

 anterior lamina, appears analogous in position to the sheath of 

 the penis in the other suborder. The vesicle is clearly 

 marked on segment 3. 



Ontogeny 



These peculiar structures develop in late nymphal life. They 

 originate out of folds and thickenings of the epidermis, formed 

 chiefly during the last nymphal stage beneath the chitinized 

 cuticle. By a careful removal of the cuticle, the underlying 

 parts may be exposed to view while still in a very rudimentary 

 condition. 



Figure 19 (m) represents the 2d segment of a nymph of 

 Libellula pulchella in the last nymphal stage in the 

 ventral view with the cuticle removed, and a cross-section of 

 the same is shown at (n). In (w), / is the anterior lamina; k, 



