THE CANADIAN ENTOMOLOGIST 143 



tuberancc, abc ut half the length of the hasal forceps arm, the paired arrange- 

 rr.ent, which shows distinctly in other species, being indicated only bv a deep 

 n-.edian cleft. The sperm ducts terminate in a pair of openings at the end of 

 the paired lobes, while from below the middle of each margin there jirojects 

 upwards and outwards as far as the base of the lobe, an elongate slender struc- 

 ture, slightly clavate near the apex. 



So very distinct are these variations in structure that they may be used to 

 separate the specie;;. Thus in Leptophlebia mollis (PI. XI, Fig. 11, 12) the basal 

 portion of the basal forceps segment is decidedly enlarged and there extends 

 from each of the divided penes a distinctly sword-shaped protrusion.. And in 

 a form clcsely resembling Leptophlebia prcepedita* (PI. XI, Fig. 13, 14) there is 

 a small, additional segment at the base of each forcep fimb, and the penes are 

 long with a proportionately smaller lateral extension. 



The Ovipositor in May-flies. 



That a modification of the abdominal segments about the egg-valve, (that 

 is ventralh" between segments seven and eight) exists in certain may-fiies, has 

 previously to the description of L. hetteni, been noted apparently by but two 

 other workers. Dr. Hagen (2) seems to have been the first to note the presence 

 of any such modification, for he states (p. 2) "Some of the females have a rounded 

 egg-\al\e at the antepenultimate abdominal plate;" and again in character- 

 izing the genus Poiamanthus which included the Leptophlebia of modern writers, 

 he states (p. 17) that the egg-valve is long. Dr. Eaton (1) in his Monograph 

 cf the Ephcmeridae, (p. 2) makes the following statement: — 



"In the female the oviducts terminate separatel\- in the joining of the 

 seventh and eighth segments; there is no real ovipositor, but in some genera 

 (e. g., Heptagenia) the apex of the seventh segment is produced into a short, 

 rounded flap, and in one Hageniihis this projection takes the form of a spout." 



In order to determine if this modification existed in any other forms, the 

 writer made an examination of several species of the genus Leptophlebia, of the 

 related genus Choroterpes, and the genus Heptagenia, all of which had been 

 collected near Ithaca, New York. In Choroterpes and Heptagenia no trace 

 of such a condition could be found, but in two species of Leptophlebia other 

 than hetteni there was a marked differentiation in the ventral structure of seg- 

 ments seven and eight between which the egg-valve opens. Leptophlebia 

 mollis shows the simplest condition in this respect. The ventral portion of 

 segment se\en extends backward very slightly, as compared with the other 

 abdominal segm.ents, to form a broad truncated lobe, imder which lie the two 

 openings of the oxiducts. Plate XI, Fig. 10 shows the ventral aspect of the 

 abdomen at this point. In the centre of segment seven are two prominent 

 conjoined ganglia in) on cither side of which lies an oviduct (o) filled with 

 eggs, opening beneath the lobe. The modification of segment eight consists 

 of two rounded chitinous ridges, converging posteriorly, covered with small 



*"This is the Leptophlebia prcepedita (?) Etn. of Needham's 'May-flies and Midges of 

 New York" (X. Y. State Mus. Bull. 86, pp. 49-.t1, 1904, PI. 11, Fig. 1, 2) and the nymph is 

 there described. The gills lack the basal tracheal stubs that are shown in both the forms figured 

 in this paper." — J. G. N. 



