Publicación del Museo de Biología de la Universidad del Zulia ISSN 1315-642X (impresa) / ISSN 2665-0347 (digital)

Anartia, 31 (diciembre 2020): 135-137

Stings by Sclerodermus wasps

Stings in humans by a parasitoid wasp of the genus

Sclerodermus (Hymenoptera: Bethylidae) in Venezuela

Picaduras en humanos por una avispa parasitoide del género Sclerodermus

(Hymenoptera: Bethylidae) en Venezuela

Charles Brewer-Carías1, Karen Brewer2 & Jorge M. González3

1Director de Expediciones, Sociedad Venezolana de Ciencias Naturales; Miembro Correspondiente, Academia de Ciencias Físicas, Matemáticas y Naturales, Caracas, Venezuela.

2 Fundacion Explora, Caracas, Venezuela.

3Austin Achieve Public Schools, Austin, Texas; Research Associate, McGuire Center for Lepidoptera and Biodiversity, USA. Correspondence: J. M. González:

Received: 23-10-2020 / Accepted: 01-12-2020 / On line: 26-02-2021

Wasps of the family Bethylidae are very diverse, with over 2,920 described species. They range from small to medium-sized, are frequently dark-colored and commonly known as flat wasps (Azevedo et al. 2018, Colombo et al. 2020). The females of many bethylids are ant-like in ap- pearance, frequently apterous, but some species are poly- morphic and females could be both apterous and macrop- terous (Richards 1939, Evans 1964, 1978, Colombo & Azevedo 2020). Flat wasps parasitize larvae of Lepidop- tera and Coleoptera and few species have been reported to sting humans, causing slight to severe pain and allergic reactions to those who suffered the wasp attack (Oda et al. 1981, Harris 1996, Lee et al. 2014, Papini 2014, Almeida 2017, Skvarla 2018). Wasps in this family, like many other wasps, have the property of inoculating an anesthetic that paralyzes their host, which is later taken as food for the wasp’s offspring (González & Terán 1996, Matthews et al. 2009, Lee et al. 2014, Almeida 2017).

Among flat wasps, the cosmopolitan genus Scleroder- mus Latreille, 1809, contains over 80 species worldwide (Almeida et al. 2017, Azevedo et al. 2018, Skvarla 2018). They are small wasps measuring 1.5 to 6 mm, and para- sitize several wood-boring beetle larvae in the families Cerambycidae, Buprestidae, Bruchidae, Bostrychidae, Te- nebrionidae, Kalotermitidae, and Curculionidae (Evans 1964, 1978, Azevedo et al. 2018, Skvarla 2018).

One of the authors (CBC) has encountered this tiny wasp species several times at his house in Caracas, Ven- ezuela. He was always taken by surprise by the tiny wasp (<3mm) (Figs. 1-2), thin as a thread, that looks like a little ant. This flat wasp species appears to be Sclerodermus nr. domesticus (Klug, 1809) based on Evans (1964, 1978). These wasps seem to be about 2.3 – 2.5 mm; with head and thorax not entirely light yellow and not uniformly cas- taneous; with mesoscutum slightly wider than long; meso- scutum and mesopleura considerably darker than prono- tum and metapectal-propodeal complex; subangular sides of metapectal-propodeal complex (Figs 1-2).

These wasps can easily move through the clothes with- out difficulty and be able to sting the bearer multiple times, most especially if the victim can hold the insect by pressing it between his/her finger and his/her skin. As a result of its defensive action, the anesthetic toxin inoculated by each sting causes a pain similar to that of a cigarette burn. Then, papules of about 5 to 10 mm in diameter and about 1 mm high appear (Fig. 3), and the stinging sensation and reac- tion remain for a few minutes. The small lumps can take up to five days to disappear. How can such a small wasp sting and be so noticeable to a human? In the case of flat wasps, the typical prey is larger, thus the wasp’s sting is efficient and powerful, making it painful to humans who have the misfortune to contact them (Gauld & Bolton 1988).

C. Brewer-Carías, K. Brewer & J. M. González


Figure 1. Apterous female of Sclerodermus nr. domesticus

(Photo: Karen Brewer).


Figure 2. Macropterous male of Sclerodermus nr. domesticus

(Photo: Karen Brewer)..


Figure 3. Leg skin of the first author of this note showing several papules up to 10 mm in diameter after three days of being stung by the flat wasp Sclerodermus nr. domesticus.

People sharing the same household with the first au- thor have frequently been stung by these tiny wasps. The ceiling structure of this house has been built with Wild Cane or “Caña Amarga” [Gynerium sagittatum (Aubl.) P. Beauv.], Poaceae). It seems that small beetles of the fam- ily Curculionidae (Scolytinae) that bore the Wild Cane

ceiling could be the hosts of this flat wasp. One day, while driving, (CBC) felt the sting and when trying to capture or stop the culprit, a wasp slit through his trousers and was able to sting him eight times on the thigh. Almost im- mediately, inflammatory reactions appeared (Fig. 3). Even though the toxins injected by the wasp might have an an- esthetic effect on its natural hosts, it certainly produces a stinging sensation. However, the wasp can move quickly and unnoticed and if unaware, it is sometimes difficult to find the origin of such stinging. Similar wasps might have produced this kind of damage and reactions, which we have experimented with while walking through the forest (Brewer Carias 2014).

Even though the wasp has been preliminarily identified as Sclerodermus nr. domesticus, some typical characteristics of that species could not be observed, but the females seem to be very similar, however, it could be a new species due to some noticeable differences, but to describe it as new, a molecular analysis is needed (W. Colombo, pers. comm.). However, this is the first time, as far as we know, that the genus Sclerodermus is mentioned for Venezuela, none- theless it has been known previously from several other American countries (Evans 1964, 1978). Physicians, der- matologists, medical doctors, and medical entomologists, as well as public health workers, should be aware of the risk of exposure to these tiny flat wasp stings.

Stings by Sclerodermus wasps


The first author is greatly indebted to his wife Fanny, his son John and his daughter Karen, who had also suffered the sting of the Sclerodermus wasp, and were able to de- sign a sophisticated photographic system (using a CAN- ON 5D-Mark II with a Macro Photo Lens MP-E 65 mm 1:2.8, and a CANON Speedlight 580EX II) that allowed them to photograph the fast-moving and elusive creatures. Thanks to Edmundo Guerrero (Universidad Central de Venezuela, Caracas) for providing us with some relevant references. We are also indebted to Wesley D. Colombo (Universidade Federal do Espírito Santo, Brazil) for iden- tifying the species and providing us with his expertise, details and helpful information about the wasp. Many thanks to Dorothy Hauswedell Whittembury for proof- reading an earlier draft of this note.


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