312 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.49. 



as in figure 111, which is passing from the teneral color pattern to the 

 adult pattern shown in figui'e 116, by the darkening of the orange 

 areas shown in the figure by stipphng. As mentioned for cervula 

 females, the adult black pattern is superimposed onto the teneral 

 black pattern by certain of the orange areas becoming brownish, 

 then smoky, and finally black. 



The follo^ving black markings appear on the mature female (see 

 figs. 85, 86, 116): 



All of the dorsal surface of head black, except pale band above 

 frons. Entire dorsum of prothorax black. Dorsum of all abdominal 

 segments black, except a narrow pale apical cross fine on segments 

 1, 7, 8, and 9. Pterostigmas smoky. The entire body and legs are 

 more or less pruinose, making a slate gray insect. The paler colors 

 of the sides of the thorax and legs and sides of the abdomen, which 

 are obscured by this pruinosity, are olive green. In very old females 

 the only fight color remaining is a brownish stripe on the outer edge 

 of the mesepisternum. In dried material the blue element in the 

 ofive green fades, leaving the insect brownish or orange with pruinose 

 and black markings. In both species the blue element, either pure 

 and by itself or in a mixed color like green, is very fikely to fade easily 

 in dried material, leaving the more permanent yellow element. This 

 is probably where the frequent dimorpliism of the female Ischnuras 

 comes in. Tlie males are seldom pure blue, but greenish — a com- 

 bination with a yeUow and a blue element. In the yellow dimorphs 

 the blue element is lacking. However, in perparva the orange 

 female is merely the teneral. 



The mature pruinose females of this species are very common, the 

 males less common, the orange teneral less common yet, and the 

 intermediate forms between the orange teneral and the adult pruinose 

 female are rare. Among 250 specimens I have 40 orange tenerals 

 and only 5 intermediate between the teneral and the pruinose. I 

 have inferi'ed that the orange teneral condition lasts the first day, 

 the change to adult occurring dm-ing the first night of imaginal life. 

 But this is merely a guess to account for the rarity of the intermediate 

 forms.* 



Nymph (figs. 122-126). — The nymph of perparva has been described 

 by Needham. The following points may serve to separate it from 

 that of cervula and other species: Length, 11-11.5 mm., gills, 5 

 extra; abdomen, 7-7.5; hind femur, 2.5; width between eyes four- 

 sixteenths of total width of head. This nymph is similar to that 

 of cervula but differs in the shorter legs, the narrower space be- 

 tween the eyes, and the obscure color patterm. In life, because of 

 the muscles and other internal organs showing through, the perparva 



1 1 have just succeeded in rearing and keeping a teneral female alive four days without change of the 

 orange color. The change in color may be due to fertilization. 



