Zatypota riverai Gauld, 1991

Sobczak, Jober Fernando, Messas, Yuri Fanchini & Pádua, Diego Galvão De, 2017, Parasitism of Zatypota riverai Gauld (Hymenoptera: Ichneumonidae: Pimplinae) on Anelosimus baeza Agnarsson (Araneae: Theridiidae) in northeast Brazil, with a description of the male, Zootaxa 4247 (1) : -

Zatypota riverai Gauld, 1991 ( Fig. 2 A–B)

Variation. The Brazilian females and males have the scape, pedicel and first flagellar segment pale ventrally.

Male ( Fig. 2 B): Body length 5.2–5.5 mm; fore wing length 4.3–4.4 mm. Similar to female in structure and color pattern, except malar space 0.4–0.6 × as long as basal mandibular width; lower face elongate, 0.9–1.0 × as broad as high (from supraclypeal suture to level of insertion of antenna). Subgenital plate transverse, about 1.7 × broader than high, with few bristles spaced medially and posteriorly; sternal apodeme broad, about 0.15 × longer than sternum (sternal apodeme plus sterno) ( Fig. 2 C); genital capsule ( Fig. 2 D-E) with paramere rounded apically, narrower than parameral lamina, 0.4 of lateroapical margin with dense bristles; volselar lamina with two or three bristles spaced longitudinally on lateroapical margin; digitus about 0.4 × length of aedeagus (including aedeagal apodeme), with tooth in apical part, rounded apically and with acuminate prolongation basally; cuspis 0.27 × length of cuspis plus volsellar lamina, with apical tooth; aedeagus (including aedeagal apodeme) 1.04 × length of paramere plus parameral lamina (incluing parameral apodeme); basal process of aedeagal apodeme about 0.15-0.23 × length of aedeagus.

Cocoon ( Fig. 1 B): Fusiform, 7.6 mm long and about 2.5 mm at its maximum diameter, with silk golden orange brownish color.

Natural history. Zatypota riverai is a koinobiont ectoparasitoid of Anelosimus baeza (Theridiidae) . All the larva (n=5) found were attached to the dorsolateral and posterior part of the host’s abdomen ( Fig. 1 ), which differs of the anterior-dorsolateral larval placement observed by Fritzén (2014) in Z. flamma on Parasteatoda sp. ( Theridiidae ). The head of Z. riverai larva points towards the posterior part of the spider abdomen. We found the parasitized spiders always on shrub vegetation, which provides a favorable microhabitat for the construction of the theridiid’s three-dimensional webs. Before killing the host, the larvae of Z. riverai induced the spider to construct a cocoon web. The general structures of normal and cocoon webs are apparently similar. However, the central region of the cocoon web exhibits a higher number of silk threads, making it denser in comparison with the normal web. Right after building its cocoon web, the spider is killed and entirely consumed by the larva, which moves to the central part of the web and begins to construct the cocoon. The larva last about eight hours to complete the cocoon construction, always in vertical orientation and at night time. After nine days, the adult wasp emerges from the apical part of the cocoon.

Figures

FIGURE 1. A) Adult female of Anelosimus baeza with a larva of Zatypota riverai attached to its abdomen. B) Three-dimensional web of A. baeza containing the parasitoid cocoon in its central region. Photographs: Jober Fernando Sobczak

FIGURE 2. Zatypota riverai Gauld, 1991: (A) habitus, female; (B) habitus, male; (C) subgenital plate (scale bar = 1 mm); (D) genitalia, lateral view (scale bar = 0.2 mm); (E) genitalia, ventral view (scale bar = 0.1 mm).