Sicarius thomisoides

It can grow between 12 and 20 mm in length, lives in desert areas of northern and central Chile and has nocturnal habits, building shelters under rocks on sandy substrate in northern Chile, it is extremely common in urban regions with a lot of household waste.[2]

Sicarius spiders have already been observed feeding on insects, scorpions and other spiders, but recently, a 20 mm long specimen of S. thomisoides was recorded in Mamiña, in northern Chile, preying on a 28 mm gecko (Phyllodactylus gerrhopygus) long. The spider was reported feeding on the fluids of the lizard's digested body, the lizard's skin was damaged and dark, indicating possible dermonecrotic effects, since enzymes of hemolytic and dermonecrotic activity were reported in Sicarius, with an action similar to that of Loxosceles.[2]

The recent study showed that the species S. thomisoides has active sphingomyelinase D, the venom of this species has effects and intensity similar to that of the dangerous Loxosceles laeta, the venom is capable of causing complement-dependent hemolysis and cytotoxic activity against human skin fibroblasts in concentrations of 10 µg, and 50 µg induces progressive dermonecrosis, basically induces hemolysis, cytotoxicity and dermonecrosis. Therefore, like Sicarius ornatus and Loxosceles laeta, S. thomisoides fulfills the toxic parameters to cause damage in humans.[3]

There has been confusion over the correct name for this species. In 1847, Charles Athanase Walckenaer published the name Sicarius thomisoides, also erecting the genus Sicarius. He based the name on illustrations he had seen in a work still in preparation and so not then published, namely a section on spiders by Hercule Nicolet in the multivolume Historia física y política de Chile. It was finally published in 1849. Nicolet called the species Thomisoides terrosus. In his earlier publication, Walckenaer had argued that Thomisoides was inappropriate as a genus name, as the species was not related to Thomisus, a crab spider. Although Walckenaer's name has priority, Thomisoides terrosus was used in subsequent descriptions, and even when the generic name Thomisoides was abandoned in favour of Sicarius, the specific name terrosus continued to be employed (e.g. in the World Spider Catalog in 2015). F.O. Pickard-Cambridge had argued in 1899 that if Walckenaer's Sicarius is used as the generic name, his specific name should be too. This argument was reinforced in 2017, and is now accepted, so that Sicarius thomisoides is the correct name for the species, which is the type species of the genus.[4]

Adding to the confusion, the specific name terrosus "was very seldom used in the literature to refer to the correct Chilean species", so that descriptions under this name may actually refer to species such as Sicarius levii.[4]