DRAGONFUES AND DAMSELFUES IN PONDFISH CULTURE. 243 



PLATHEMIS LYDIA. 



The females of tliis species remain at some distance from the water, except at the time of ovipositing ; 

 one caught a quarter of a mile from the ponds deposited eggs freely on July 25, which began to hatch 

 August 2, and were all hatched by August 9. 



The Egg. — These eggs are elongate elliptical and rather pointed at both ends, just twice as long as 

 wide, the two diameters being respectively 0.60 mm. and 0.30 mm. The neck is as wide at the base as it 

 is high, with a distinct segmentation near the tip, the lati er being undivided ; there is no process on the 

 posterior end of the egg. 



The Nymph.— The general color of the nymph is yellowish white, with light-brown markings. On 

 the center of the dorsal surface of the head is a longitudinal, club-shaped, brown area and on either 

 side a broken semicircle; there is a large, irregular, brown spot in the center of the posterior thorax and 

 anterior abdomen, and another smaller spot over the posterior end of the respiratory system. The eyes 

 are dark brown, with black, retinal spots; the tracheal system is yellowish brown. The head is a trifle 

 wider than long and not narrowed behind the eyes; the thorax is two-thirds as wide as the head; the 



Figs. 52 to 54. — Development of Plathemis lydia: 52, egg; 53, mask of newly hatched nymph; 54, newly hatched nymph. 



abdomen the same width as the head, sharply pointed posteriorly, with strongly convex, lateral margins 

 and no color markings except the two spots already noted. The base and basal joint of the antennae are 

 whitish; proximal end of second joint and the whole of the third joint light gray, distal part of second 

 joint white. The legs are light gray and white; the tips of the posterior processes of the abdomen are 

 dark brown; the terga of the thoracic segments are light gray. 



The Mask. — Mentum twice as wide as long, with convex sides; distal margin two and a half times 

 the proximal; one lateral seta near the base on each side and two marginal setae; three mental setae on 

 either side of the center in a curve concave to the midline; two small spines at the center of the 

 distal margin. Lateral lobes one-half longer than wide; two setae on the outer border, none on the 

 blade; raptorial seta just reaching the tip of the movable hook, the latter short and stout; distal 

 margin with seven teeth reaching nearly the entire width, the third tooth the longest. 



EPICORDULIA PRINCEPS. 



The eggs of this species are laid in long, jelly-like strings, similar to those of Tetragoneuria. Some 

 of these strings were obtained from the leaves of Potamogeton illinoiensis in pond 3D on August 9, 1917; 

 but, of course, there was no way to tell when they were laid; they began to hatch within a day or two. 



The Egg. — This egg is the largest of any here described, being 0.72 mm. long and 0.40 mm. wide. 

 The neck is a minute process of the same height and width, without segmentation, and there is no process 

 on the posterior end of the egg. 



