428 



real suture between the two. Cephalad of the propleural suture is a 

 somewhat triangular area, the proepisternum (peps), the cephalo- 

 ventral angles of which are drawn out and extend ventrad in front of 

 the procoxae. The cephalo-ventral arms of the proepisterna are fused 

 with the propreepisterna. Between the dorsal triangular portion of 

 the preepisterna and the microepimera is a small, much-wrinkled area, 

 which appears to be composed of a number of sclerites. This, how- 

 ever, belongs to the proepisternum. 



Prosternum (Figs. 2y, 29). — The cephalo-ventral arms of the 

 episterna, as described above, extend ventro-cephalad and become ap- 

 proximate but not quite contiguous on the ventro-meson. Caudad of 

 the approximated ends of the episterna there is a large shield-shaped 

 ventral sclerite the caudal margin of wdiich is concave. This is the 

 fused sternum and presternum (prst). The caudo-lateral angles are 

 usually acute, and at the tips of these angles are found the deep in- 

 vaginations of the furcae (fi). Caudad of the sternum and between 

 the furcae is a heavily pigmented chitinized area, the sternellum, which 

 extends about as far caudad as the caudal margins of the coxae. In 

 some cases there is within the sternellum an elliptical or oval depressed 

 area much resembling a true sclerite. This is a secondary formation. 

 On each side of the meson, caudad of the sternellum, is a heavily chi- 

 tinized bar which extends latero-caudad and is attached to the meso- 

 thorax. These bars represent the furcella (fl). 



Mesothorax and Mctathorax (Figs. 40-47). — This division of the 

 thorax bears the two pairs of wings and the second and third pairs 

 of legs. A glance at the mesothorax and metathorax of any dragon- 

 fly will show that the wings, instead of being borne on the mid-dorsum 

 of the thorax, are situated far to the rear and are inserted just above 

 the cephalic margin of the first abdominal segment. This change in 

 wing position has brought changes in the structure of the thorax as 

 a whole, including the reduction of primary sutures and the appear- 

 ance of many secondary ones, and as a result the external thoracic 

 skeleton of Odonata is as complex as that of the highly specialized 

 Hymenoptera and Diptera. 



Mcsnotimi (Figs. 41, 44, 46, 47). — As has been mentioned in 

 the nymphal description, the mesepisterna are approximate on the 

 dorso-meson. In the adult the two have united and fused, a single 

 suture being left, extending from near the caudal margin of the pro- 

 notum to the wing bases. In some cases this suture is slightly elevated, 

 forming a carina (dc), but it is often flattened at the point of fusion 

 of the two pieces and the suture nearly obliterated. Cephalad of the 

 dorsal carina there is a small somewhat rhomboidal area, the prescutum 



