Latrodectus geometricus C.L. Koch

Al-Jahdhami, Ali, Al-Raeesi, Ali & Al-Rashdi, Said, 2022, First Records of Black Widow Spider Latrodectus Walckenaer (Araneae: Theridiidae) in Oman, EntomoBrasilis (e 1007) 15, pp. 1-3 : 2-3

Latrodectus geometricus C.L. Koch Figure (2)

Examined specimens. 1 ♀ Dhofar, Taqah, Ain Athum 9. iii.2020, leg. Ali Al-Jahdhami ; 1 ♀. Samad Ahan, Ba ad, 14.vi.2020, leg. Ali Al-Jahdhami .

Biological characteristics. The morphology of females from Oman matches (color pattern, number of coils of copulatory ducts) the description of KNOFLACH & HARTEN (2002). Spermathecal ducts of the female vulva with three loops [see KNOFLACH & HARTEN (2002) for the duct figures]. The color pattern of L. cinctus strongly resembles L. hasselti Thorell and L. renivulvatus ; these three species can be diagnosed by the pattern of their abdominal setae and minor differences in genital organs ( ZAMANI et al. 2014). The coloration of opisthosoma varies dramatically in adult females from dark brown/black without patterns to brown/black with different longitudinal/transversal red/orange stripes ( ZAMANI et al. 2014). All examined females have a long orange median band on the dorsum of opisthosoma and their tarsi is dark brown or black. However, we believe there are some color variations among the other specimens since we did not confirm the identification.

Natural history. These specimens were collected in urban areas, around homes, gardens, and green-houses. The webs were built close to the ground and were rarely observed built up to one-half meter above the ground.

Poison. The poison of L. cinctus has been not studied ( LOTZ 1994). A study from Iran described the clinical treatment of a bite of L. cinctus . This bite of L. cinctus can cause a slight burning sensation turning into a painful feeling after 15 min, then sweating and spreading of the pain from the bite site to the upper limbs ( NEJATI et al. 2022). Anti-venom injection Biological characteristics. The females of L. geometricus from Oman match the morphological description of KNOFLACH & HARTEN (2002). Color Pattern: carapace with darkened margin and median band, the sternum is brown with the tapering median band. Legs are brown with apical femora, patella, and tibiae black. Opisthosoma is a light brown and dorsal pattern consisting of three rows of dark and white patches. Two paramedian rows of dark spots are surrounded by white patches, which extend laterally and anteriorly. The venter of the opisthosoma has a distinct red hourglass marking. The ducts form a double helix and four outer coils, [see KNOFLACH & HARTEN (2002) for the duct figures].

Poison. KNOFLACH & HARTEN (2002) reported that poison effects of L. geometricus are not as severe as those of its congeners. The poison symptoms by L. geometricus were relatively mild and restricted to the bite site and surrounding tissues ( MULLER 1993). The LD50 value for mice is 233 micrometer of protein and the LD50 per spider is 56 micrometers only ( MULLER et al. 1989). The spider is considered an unaggressive species ( BAERG 1959).

Natural enemies. parasitoids of the genus Eurytoma ( Hymenoptera : Chalcidoidea: Eurytomidae ) have been observed emerging from the egg sac of L. geometricus in specimens collected from the Dhofar region. Eurytoma arachnovora Hesse was reported as parasitoid during the rearing of L. geometricus ( BAERG 1959) . Eurytoma abalosi De Santis and Tetrastichus sp. ( Hymenoptera : Chalcidoidea: Tetrastichinae) frequently parasitized the egg sacs of L. geometricus in Argentina ( ABALOS & BAEZ 1967).

Distribution. Latrodectus geometricus occurs in all continents and most commonly in Africa where it is suggested to be native ( LEVI 1959). It is recorded from Yemen, Socotra ( SIMON 1890; POCOCK 1903), and Saudi Arabia ( LEVI 1959) in the Arabian Peninsula. This is the first record for Oman and occurred in both northern and southern of Oman.