Two new pseudoscorpions: Tyrannochthonius eua & Nesocheiridium onevai

Pseudoscorpions are a type of arachnid, meaning that they are not insects, but are closely related to spiders. They are cryptic animals, living amongst leaf-litter, under rocks, within compost piles, under bark and within decaying wood, in caves, and in various vertebrate nests. We know little about these tiny organisms and they are sometimes referred to as ‘neglected cousins’ of the spiders. They are named “Pseudo” scorpions because they have pincers that resemble scorpions, but do not have a tail and stinger. They can be found anywhere from a tree canopy, to somewhere in your home where they feed on the larvae of some household pests. They can also be found in leaf litter, where they feed on other tiny arthropods. Males use chemicals known as pheromones, and a fancy dancing behaviour, to attract females to mate. These arachnids construct a silken cocoon which they use to protect themselves during the winter. Pseudoscorpions occur all over the planet. Both new species were named after the Polynesian islands on which they were found. 

For the experts: The genera Tyrannochthonius Chamberlin, 1929 and Nesocheiridium Beier, 1957 are recorded from the Tonga Islands, Polynesia, for the first time. Tyrannochthonius eua sp. nov. is described from the island of Eua. Nesocheiridium onevai sp. nov. is described from the island of Onevai. This is the first discovery of a representative of the genus Nesocheiridium in more than 60 years. The holotype of the type species, Nesocheiridium stellatum Beier, 1957, is redescribed, allowing a better understanding of this poorly known genus. The genus Nesocheiridium is diagnosed by the following combination of characters: integument coarsely granulate, dorsally granulo-reticulate; vestitural setae either relatively long, with a leaf-like outline, or arcuate with a small spine; cucullus short; only 10 abdominal tergites visible in dorsal view; cheliceral rallum of four blades; venom apparatus present in both chelal fingers; fixed chelal finger with granulate swelling mesally and seven trichobothria; trichobothria ib and ist located distad of granulate swelling; eb and esb situated close together at the base of the finger; moveable chelal finger with two trichobothria.