NORTH AMERICAN ODONATA. 189 



structure of the vulvar lamina as an ovipositor ; this may be termed 

 endophytic ovipositioii. In the other subfamilies no ovipositor exists, 

 and the eggs are merely dropped into water or attached by a gummy 

 substance to the surfaces of submerged bodies; such oviposition may 

 be styled exophytic. In either of these cases the male may or may 

 not retain his hold of the female's prothorax by his appendages 

 during oviposition. 



1. Endophytic ovipodtlon. — A favorable opportunity enabled the 

 writer to see, in Argia violacea, an Agrionine, the sharply pointed 

 and roughened ends of the halves of the vulvar lamina cut into 

 plant tissue and push the eggs into the incisions. The valves assist 

 in the deposition and probably also steady the abdomen. The first 

 eggs in this case were laid just below the water's surface, the female 

 gradually descending and inserting the eggs farther and farther 

 downwards. The laying of the eggs in plants below the surface, 

 necessitates the descent of the female into the water, so that she may 

 be completely submerged, as the writer has witnessed in Enallagma 

 exsidans, and as has been observed in different species of Agrionine 

 and Aeschninse by many others. When the male retains his grasp of 

 the female's prothorax during oviposition, and the female continues 

 to descend, he usually loosens his hold and separates from the female to 

 avoid being dragged into the water. VouSiebold saw the male of Lestes 

 sponsa also descend below the surface with the female, and the writer 

 has witnessed the same phenomenon in three different pairs of Enal- 

 lagma exsidans. When immersed, both male and female are encased 

 by an envelope of air. After eggs have been deposited in a plant, 

 by holding the latter between one's eyes and the light, the eggs can 

 usually be seen lying between the veins of the leaf-blade. While 

 the male and female of endophytic groups remain attached during 

 oviposition to a greater extent than in the exophytic groups, yet 

 Anax Junius and Ischnura vertiealis have been seen by the writer at 

 one time to lay the eggs without the attachment, or even presence 

 of a male, and at other times to lay them with the male attached. 



2. Exophytic oviposition. — The feuiale repeatedly dips the end of 

 her abdomen into the water at a rate, in Flathemis trimaeulata, of 

 120-150 dips per minute. At other times she strikes the water with 

 her abdomen with such force as to fasten the eggs upon the vertical 

 surface of rock (Buckhout). The eggs of this group are found to 

 be covered with a transparent substance which causes them to ad- 

 here to adjacent objects. The dipping of the female's abdomen 



TRANS. AM, ENT. SCO. XX. AUGUST, 1893. 



