ODONATA, 



11 



Libelliila pulchella, and Fig. ^^, a. Libellida qtiadrupla, both 

 natural size, it will be seen that the same useful structure 

 has been developed in different species as adaptations to 

 the similar habits of these insects. 



Besides the compound eyes (PI. III., Fig. 34, ey, 

 p. 73) there are three ocelh. The largest (Fig. 34, 

 oc) is in the median line, below the chitinous promi- 



Fig. 33, a. 



nence, which rises from the upper part of -the head, 

 and in a front view cuts off the junction of the com- 

 pound eyes. The two small oceUi (Fig. 34, oc') are 

 on each side of this prominence. The foremost ap- 

 pendages of the head are the short, bristle-like antennae 

 (PI, III., Figs. 32, 34, at). Their minute size is in 

 striking contrast to the immense size of the compound 

 eyes. Below the clypeus (Fig. 34, r/) and labrum 

 {la) are the deeply notched mandibles (PI. III., 



