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: 715-716

publication ID 10.1111/j.1096-3642.2007.00314.x

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Description ( Fig. 1C View Figure 1 )

Testis: Each testis is spindle-shaped, not divided into follicles ( Matsuda, 1976), but comprising bundles of spermatozoa ( Mead-Briggs, 1962).

Epididymis: The outer tissue of the testis is enclosed posteriorly in a coiled tubular epididymis and probably functions as the seminal vesicle ( Mead-Briggs, 1962).

Vas deferens: Each vas deferens leads posteriorly from the epididymis and the two are united at midlength in a common sheath. After uniting, the common duct arches anteriorly and loops around the median accessory glands, to which it is loosely attached (Mead- Briggs, 1962). This duct empties directly into the fused ejaculatory ducts.

Accessory gland and seminal vesicle: Paired accessory glands, sometimes comprising two pairs of lobes of unequal sizes, separately enter the ejaculatory duct prior to the ejaculatory bulb (see Fig. 1C View Figure 1 , right). The glands are composed of columnar epithelial cells and have a secretory function ( Günther, 1961; Mead- Briggs, 1962; Matsuda, 1976; Cheetham, 1988: fig. 84). No seminal vesicle has been identified.

Ejaculatory duct: The paired vasa deferentia become continuous with the paired, ejaculatory ducts, which unite at the level of the ejaculatory bulb ( Mead-Briggs, 1962; Cheetham, 1988).

Ejaculatory apodeme, sperm pump, and aedeagus: There are two sperm pumping devices in Siphonaptera   ( Günther, 1961; Cheetham, 1988; Hünefeld & Beutel, 2005). The proximal pump is termed the ejaculatory bulb (sometimes the walls bear an ejaculatory sclerite) and is separated from the base of the endophallus ( Günther, 1961: fig. 26; Mead-Briggs, 1962). Distally beyond the gonopore is the second pumping device, a musculated chamber ( Günther, 1961; Cheetham, 1988; Hünefeld & Beutel, 2005). The aedeagus emerges as a narrow tube, bearing a pair of apical hooks or crochets ( Matsuda, 1976). A pair of penis rods lies within the endophallus and at least one can be protracted from the aedeagus to enter the female bursa copulatrix ( Matsuda, 1976).

Remarks: See the remarks under Mecoptera   for a discussion of the phylogenetic position of the Siphonaptera   . The vasa deferentia are looped anteriorly, as in many lower Diptera   and Mecoptera   . However, they do not enter the accessory glands anteriorly, but empty directly into the ejaculatory duct.

Hünefeld & Beutel (2005) also did not regard the sperm pump of Siphonaptera   as being homologous with that of Mecoptera   or Diptera   . The proximal pump may include an ejaculatory sclerite, which is withdrawn anteriorly from the base of the endophallus.