. Bulletin - New York State Museum. Science. AQUATIC INSECTS IN NEW YORK STATE 231 tions of imagos. I present a key based chiefly on the form of the male appendages, which will be sufficient, I trust, for the deter- mination of species. Of these nine species I have reared five. I regret to acknowledge, after prolonged study of them, that I find them well nigh indistinguishable specifically. Aside from slight and inconstant differences in size and a few very minor structural characters, they are all alike. I will give therefore a general description of them and supplement it with a tabular stat
. Bulletin - New York State Museum. Science. AQUATIC INSECTS IN NEW YORK STATE 231 tions of imagos. I present a key based chiefly on the form of the male appendages, which will be sufficient, I trust, for the deter- mination of species. Of these nine species I have reared five. I regret to acknowledge, after prolonged study of them, that I find them well nigh indistinguishable specifically. Aside from slight and inconstant differences in size and a few very minor structural characters, they are all alike. I will give therefore a general description of them and supplement it with a tabular statement of such differences as I have thus far been able to discover between them. Nymph. The nymph of Lestes is exceedingly long and slender, with wide head, deep thorax and slender, cylindiic ab-. Fifi-. 7 Nym])h of Lestes r ec t a n g-u 1 a r i s: A, gills, more eularg-ed domen, bearing linear-oblong gill plates. Head twice as wide as long, only moderately prominent at the front; eyes prominent, rounded, directed somewhat anteriorly; hind angles low, well rounded, with a shallow wide notch between them on the hind margin; antennae longer than the head, with the segments in- creasing in length to the third, and decreasing thereafter to the tip, seven-jointed. Labium [, ] long and exceedingly slender, the hinge reaching as far posteriorly as the hind legs, but dependent, and not closely applied to the ventral surface of the body; mentum linear to the suddenly dilated, and spoon- shaped tip; median lobe moderately prominent, with a closed median cleft which extends as far proximally as the level of the bases of the lateral lobes; mental setae well developed; lateral lobe very complicated [see , ], bent almost at a right angle Just beyond its base, having a A'ery large movable hook, be- yond the base of which the distal portion is cleft into two parts, the inner one of which bears the end hook and the usual inner series of teeth, these being very numerous, reg
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