PACHYNEURIDAE, Schiner, 1864

Sinclair, Bradley J., Borkent, Art & Wood, D. Monty, 2007, The male genital tract and aedeagal components of the Diptera with a discussion of their phylogenetic significance, Zoological Journal of the Linnean Society 150 (4), pp. 711-742 : 720

PACHYNEURIDAE

Description ( Fig. 3D )

Testis: The testis is slender, sac-like, rounded anteriorly, and tapered posteriorly.

Epididymis: Not differentiated.

Vas deferens: These ducts extend posteriorly to the base of a large accessory gland complex and then arch and unite weakly medially ( Fig. 3D ). The vasa deferentia extend anteriorly as twin ducts closely applied to each other, before entering the anterior apex of the accessory gland complex. Layers of spermatozoa filling the entire ducts were observed in fresh specimens.

Accessory gland and seminal vesicle: A single large, rounded gland is present in Pachyneura fasciata Zetterstedt , referred to here as the accessory gland complex. The gland remains divided medially and at least two distinct chambers are visible on each side. No seminal vesicle is differentiated.

Ejaculatory duct: This duct remains paired upon exiting the accessory gland complex and is relatively short, slightly longer than one-half length of the accessory gland complex.

Ejaculatory apodeme, sperm pump, and aedeagus: The external genitalia of Pachyneura fasciata was illustrated in Wood (1991: fig. 7) with the various components shown in different colours. The ejaculatory apodeme is a small concave plate fused to the anterior end of the mostly sclerotized aedeagus and consequently the sperm pump is reduced. The apex of the aedeagus (phallotrema) is U-shaped and quite narrow.

Remarks: The male genital tract of Pachyneura Zetterstedt is here described and illustrated for the first time. The ejaculatory apodeme no longer functions as a piston in Pachyneura , but probably assists in drawing the spermatophore out and into the female genital chamber as in Bibionidae (see below).

Figures

Figure 3. Male internal reproductive organs (dorsal view). A, Hesperinus rohdendorfi (Hesperinidae). B, Plecia membranifera (Bibionidae). C, Bibio flavihalter (Bibionidae), left vas deferens and testis removed (based on the specimen photographed in Fig. 4A). D, Pachyneura fasciata (Pachyneuridae). acc gl cplx, accessory gland complex; ej dt, ejaculatory duct; tes, testis; vas df, vas deferens. Scale bars = 0.1 mm.