414 



tion of the epicranial suture, which is a Y-shaped line on the dorsum 

 of the head, near the caudal mar.s^in. Sutures are wanting, separating 

 vertex from occiput, occiput from postgenae, and postgenae from 

 genae. The vertex occupies that part of the dorsum of the head cap- 

 sule caudad of the arms of the Y ; and the occiput and postgenae 

 together, the portion of the caudal aspect of the head not occupied by 

 the occijiital foramen and the compound eyes. The genae are the areas 

 mesad of tlie \entral margins of the compound eyes. They fuse with 

 the postgenae (Fig. 7, pg) near the ventral margin of the head. 

 Extending caudo-dorsad on the caudal aspect from the ventral articu- 

 lations of cacli mantlilile, there is a distinct ridge which disappears 

 near the middle of the head. The trochantins of the mandibles are 

 present as indistinct triangular areas laterad of the bases of the mandi- 

 bles (Fig. 7, tm). 



Co))ipoiim{ Eyes. — The comjioimd eyes of the nymphs, like those 

 of the adult, are very large. They occupy perhaps one-third of the 

 dorsal surface of the head, nearly the whole of the lateral surface, 

 and part of the ventral. Tlie facets arc hexagonal antl similar to those 

 of other insects. 



Ocelli. — The ocelli are wanting during nymplial life, l)ut in the 

 later stages the adult ocelli may be seen through the transparent cuticle 

 of the dorsum of the head. Thus it often appears as if the nymph 

 had ocelli when in reality there are none present, as: can be proved by 

 an examination of tlie final exuvium, or l)v dissection. 



Antennae. — The antennae, in all full-grown nymphs, consist of 

 seven segments. The distal segment is short in most species and the 

 connection Ijetween it and the preceding one is frequently obscure, so 

 that it seems as if the ai)pendage had only six segments. The first 

 segment is usually thicker than the remaining ones, and in the 

 Agrionidae is as long as all the rest of the segments together. In the 

 Ci>enagrioni(lae, the third segment is the longest and each of the seg- 

 ments distad of it is shorter than the segment preceiling. The two 

 proximal ones are not constant in length but are alwavs shorter than 

 the third. 



Mandihle.w — Tlie mandibles are normally hidden from sight by 

 the large labium and the flap-like labrum. They are located on the 

 ventral surface of tlie head and are well formed for mastication. They 

 are irregular in outline, though somewhat rectangular, bearing four 

 short, strong teetli along the distal margin and several smaller teeth 

 mesad ami proximad of these. 



Maxillae. — The maxillae (Fig. 22) are attached to the ventral 

 surface of the head and tlie following parts are distinguishable: a 



