The sexual behaviour and genital mechanics of three species of Mynoglenes (Araneae: Linyphiidae)

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Abstract

The sexual behaviour and genital mechanics of three species of Mynoglenes Simon 1905 are described, and compared with those of other species of Linyphiidae. A brief courtship is followed by sperm-web building and palpal induction by the male, the latter processes resembling those of Erigoninae. No intromissions are performed prior to induction. Courtship comprises elements common to both Erigoninae and Linyphiinae. The male palpal organ is simple, with a small curved paracymbium, an undivided suprategulum continuous with the tegulum, a large funnel-shaped conductor derived from the duct membrane, a radical component continuous with a filiform embolus, and lacks a lamella, terminal apophysis or other accessory processes of the embolic division: it is erigonine in character. The vulva comprises a well-developed scape of linyphiine type, and large atria which lead to spiral bursae terminating in small receptacula. Locking of the genitalia is achieved by the suprategulum catching in a socket on the ventral surface of the scape while the conductor lodges in the corresponding atrium so that suprategulum and conductor grip the vulva like callipers. Locking is sustained, and during its course the embolus is thrust through the channel formed by the conductor deep into the vulva and withdrawn many times. The mechanics of this unusual form of intromission are discussed, and shown to require three separate stages of haematodochal expansion; the first precedes locking, which is achieved by a backwards stab of the partially-expanded palp. The subocular secretory sulci present in both sexes play no role in sexual behaviour and are not used to engage the chelicerae of either partner, despite aggressive interactions in the early stages of courtship. The comparative aspects of these observations are discussed, with particular reference to the mixture of erigonine and linyphiine characters shown by Mynoglenes. It is argued that Mynoglenes and its allies, including the central African genera Afroneta and Trachyneta, constitute a relict group which preserves some ancestral linyphiid characters, and that subocular sulci may have been re-located in the course of evolution to provide the post-ocular sulci of male Erigoninae. In some genera, the latter are known to be gripped bv the females' chelicerae during copulation.

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