Dresserus Simon

Miller, Jeremy A., Griswold, Charles E., Scharff, Nikolaj, Řezac, Milan, Szűts, Tamas & Marhabaie, Mohammad, 2012, The velvet spiders: an atlas of the Eresidae (Arachnida, Araneae), ZooKeys 195, pp. 1-144 : 32-33

Dresserus Simon

Dresserus Simon 1876: LXXXVII [87]. Type species Dresserus fuscus Simon, 1876.

Note.

Dresserus contains 24 recognized species from eastern and southern Africa ( Platnick 2011). We examined specimens of multiple unidentified Dresserus species. O bservations of the male plus the female spinneret spigot morphology is based on specimens from Mazumbai, West Usambara Mts., Tanzania (CASENT 9025746, CAS and CASENT 9025747, CAS); other observations of the female based on specimens from Klein Kariba (CASENT 9025745, CAS) and Drummond (CASENT 9037024, CAS), South Africa; other observations of the male based on specimens from Manga Forest Reserve, Tanzania (Frontier Tanzania, ZMUC), Hluhluwe Game Reserve, South Africa (TM 19739, TMSA), and Witbank, South Africa (TM 19738, TMSA).

Diagnosis.

Distinguished from other eresids except Gandanameno by the position of the PLE which are both advanced (<0.28) and widely spaced (PER/AER> 0.95; Fig. 8J); other eresids with advanced PLE (e.g., Stegodyphus , some Paradonea ) have them closer together (PER/AER <0.90) than the ALE (Figs 10B, 11B, D, F, H, J, L). Generally distinguished from other eresids by the distinctive 4-part cribellum (Fig. 36F), although some Gandanameno specimens show signs of this characteristic. Males distinguished from other eresids by the prominent tubercles bearing the ALE (Figs 8J, 33A), which are much more pronounced from those in other genera with ALE tubercles (e.g., Stegodyphus , some Paradonea ). Further distinguished from other eresids except Gandanameno by the more or less ventral-dorsal axis of the palpal bulb with the embolus encircling the ventral part (Figs 12 G–I, 33 I–K, 34 A–D; proximal-ventral in other eresids with the embolus encircling the distal part); distinguished from Gandanameno by the smooth conductor (Fig. 34C, D; fringed in Gandanameno , Fig. 55C, E). The cephalic region may be wider than long (e.g., TM 19738, TMSA, Frontier Tanzania, ZMUC) or longer than wide (e.g., TM 19739, TMSA). Female further distinguished from other eresids except Gandanameno and Eresus walckenaeri by the copulatory openings, which are broadly separated by hirsute cuticle (Figs 16C, 37D; separated by a glabrous median lobe in other eresids, e.g., Figs 16B, 29C); Gandanameno and Dresserus together distinguished from other eresids including Eresus walckenaeri by the vulva, which have the spermatheca extending anterior of the spermathecal heads, together subtended by helical copulatory ducts (Figs 16F, 37E; other eresids have the spermathecal head anterior, spermatheca posterior, and copulatory ducts other than helical), and by the subdivided PMS (entire in other eresids) with numerous short, conical, cylindrical(?) gland spigots (Fig. 36C, D; this spigot morphology absent in other eresids); distinguished from Gandanameno by the somewhat less prominent paired atria and possibly by having a single loop of the copulatory duct (Fig. 37E; three in Gandanameno , although this character has been investigated in few Dresserus species).

Distinguishing species.

Thetaxonomic literature on Dresserus is fragmentary and rarely comparative. This genus is ripe for revision. We have been unable to confidently assign species names to the specimens used in this study. Lehtinen (1967: 231) indicated that he was working on a taxonomic revision, but none was ever published. According to him, all but one of the described species (including the type species) had been checked and verified as congeneric based on primary types and other material.

Natural history.

Known from Savanna, stony semidesert, and forest habitats. They build a silken tube under stones. Prey is mainly beetles (Milan Řezáč, personal observa tion). Clutches consist of tens of juveniles (Martin Forman, personal observation of Dresserus kannemeyeri ). Juveniles do not feed on their mother’s corpse. Mature females can live for several years in captivity and can produce a number of sequential clutches (Martin Forman, personal observation of Dresserus kannemeyeri ).