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VIII. Ronarls upon the Homologies of tJie Ovipositor. 

 By A. E. Eaton, B.A. 



[Eead 17th February, 1868.] 



Reading in the Proceedings of the Society (Proc. Ent. 

 Soc. 1867, p. Ixxxv), that the Homology of the Ovipo- 

 sitor formed the subject of a discussion at the April 

 meeting of 1867, and seeing that no definite conclusion 

 was arrived at upon the matter, I have ventured to put 

 together a few observations relating to the question, 

 hoping that they may go a little way towards its solution. 



I shall take as a criterion the ovipositor of the adult 

 Agrion, because in this genus, the elements composing 

 that organ remain free during the whole course of their 

 development. There are three pairs of these elements 

 in Agrion. One pair constitutes the terebra, the next 

 the inner valvulse, the third the outer valvulae, otherwise 

 called the valvulae vaginales. The terebra is formed of 

 long ensiform pieces, {ogdo-tergo-rhahdites, Lacaze-Du- 

 thiers) denticulated towards the apices, which arise from 

 the middle of the posterior edge of the eighth abdominal 

 ventral arcus. It produces a somewhat carinate ridge on 

 the under-surface of the apparatus. From behind and 

 above it, near the centre of the base of the ninth abdo- 

 minal ventral arcus {sternite, Lac.-Duth.) spring the 

 linear inner valvulae, [ennato-sterno-rhahdites , Lac.-Duth.) . 

 Exterior to these, from a longitudinal base, and from the 

 same segment, the lamelliform, truncate, and slightly ap- 

 pendiculated valvulae vaginales [ennato-episternites, Lac.- 

 Duth.) grow out : these with the terebra enclose the in- 

 ner pair. [I drew up this description, and those after- 

 wards given, from moistened cabinet specimens.] In 

 Caloptenjx Q.ndi Libellula the inner valvuliB are sub-obsolete, 

 if not entirely suppressed. 



The egg-valve of certain Ephemeridce is not specially 

 homologous with any of the elements of the ovipositor 

 of Agrion. It is just possible that it may exhibit the 

 same general homology as the terebra; for in Lepto- 

 phlebia vespertina, Lin., [cincta, Retz.), it is merely a 

 minute projection from the middle of the apical border of 

 the seventh ventral arcus. Its special homologue seems 

 to be a production from the lamina subgenitalis of Deti- 



TRANS. ENT. SOC. 1868. — PART I. (aPEIL) . 



