i} 
structures are the evidences of the strongly developed first pair 
of hamules which come from the posterior portion of the an- 
terior lamina. Comparisons of this figure with the imago will 
bear out this conclusion. 
_Figure 21 represents the conditions found in Peri- 
_ ple in structure and has already been described, special 
attention being called to the notches at the sides, and to 
REPORT OF THE STATE ENTOMOLOGIST I907 255 
: specialized Libellulinae there are scarcely any indications of 
these parts in the nymph externally visible, but they are easily 
recognized in most Corduline nymphs. 
In (2) two structures are noted meeting in a median line and 
apparently a part of the lamina anterior to them. ‘These 
Comparative anatomy of adult forms 
Let us now proceed to a more careful examination of these 
parts and their relations in the several major groups of Odonata, 
beginning with a generalized representative of the Libellulinae. 
themis. The anterior lamina here (figure 21 ) J; is sim- 
the lateral divisions marked k, for these indicate the 
source of the anterior pair of hamules. ‘The hamule h is attached 
anteriorly to the portion of the framework which passes forward 
under the anterior lamina, as well as to v which here is only a. 
line of chitin passing posteriorly to the sheath s. This line of 
chitin is to be found in all other forms in both suborders and it 
seems to be a part conjoining the rear ends of the second pair of 
-hamules. Wherever the hamules are well developed, this line of 
chitin is well developed, as will be shown farther on. s is the 
sheath of the penis which is transparent and poorly chitinized, 
another characteristic of this family. This sheath is attached at 
two points to the line v connecting the hamules, as well as to the 
anterior portion of the U-bar where it begins to curve upwards. 
In Nannothemis, Perithemis and Celithemis these condi- 
tions were found to be approximately the same. In the last was 
found the least chitinized condition of the portion of the frame- 
work marked wv connecting hamules or either side of- the 
sheath. In all other forms examined it was well developed and 
in some it was very thick and strong. As far as complexity or 
specialization of parts is concerned, the author concludes that 
