Neaetha wesolowskae

Neaetha wesolowskae is a species of jumping spider in the genus Neaetha that is endemic to Thailand. The Neaetha spider that has been found most easterly, it lives in rainforests. First described in 2020 by Barbara Patoleta & Marek Żabka, the spider is named for the Polish arachnologist Wanda Wesołowska. It is small with a brown carapace between 0.86 and 1.49 mm in length and an abdomen that is between 0.97 and 1.2 mm long. The female is smaller than the male and has a pattern of spots rather than lines on its abdomen. The female is hard to tell from other members of the genus but can be differentiated by its copulatory organs. Its epigyne has ovoid, rather than crescent-shaped, copulatory openings and spermathecae that are separated rather than lying together. The male has an embolus that is unusually crescent-shaped.

Taxonomy
Neaetha wesolowskae was first described by Barbara Patoleta & Marek Żabka in 2020. It was allocated to the genus Neaetha, which itself had been first circumscribed by Eugène Simon in 1884. The genus is named for two Greek words, néos, which means new, and théa, which can be translated as aspect. The species is named for the Polish arachnologist Wanda Wesołowska.

The species is hard to distinguish from others in the genus, leading to Patoleta and Żabka suggesting that understanding the relationships between the different species will require study of the genes rather than their physical attributes. This confusion spreads to the genus, as Neaetha spiders are externally similar to other genera, including Bianor, Harmochirus. However, subsequent study has proved that they are only distantly related. A DNA analysis study undertaken by Wayne Maddison and Marshall Hedin identified that the genus is most closely related to the g|enus Salticus. It has also phylogenetic similarities with Carrhotus and Hasarius, amongst other genera of jumping spiders. The genus was placed in the subtribe Harmochirina in the tribe Plexippini by Maddison in 2015. These were allocated to the clade Saltafresia. The subtribe is divided into harmochirines and pellenines, and the genus is allocated to the latter group, which is characterised by living on the open sunny ground.

Description
Neaetha wesolowskae is a small spider with a body divided into two main parts: a broad cephalothorax and an oval abdomen. The male has a rather high carapace, the hard upper part of the cephalothorax, that is 1.49 mm long and 1.3 mm wide. It is robust, and with a distinctive sloping thorax. The carapace is brown and covered in white scales with a distinct fovea, or depression, in its middle. There are more scales on the sides but none on the sternum, the underside of the cephalothorax, which is light brown. The spider has a darker eye field. The spider's face, or clypeus, is brown with light scales on the bottom. The chelicerae are brown, with two forward teeth and one rear tooth. The rest of the mouthparts, including the labium, are also brown, but have light tips.

The abdomen is 1.2 mm long and 0.71 mm wide and has a pattern of three wide brown stripes on the top. It is covered in brown and whitish scales and hairs, the hairs being longer at the front. The underside of the abdomen is light grey with a pattern of darker spots. The spinnerets are light brown and the legs are brown. The first pair of legs are wider than the others. The pedipalps are hairy. The palpal tibia has a long narrowing projection, or tibial apophysis, that has a pointed and slightly bent tip. The palpal bulb has an ovoid tegulum with a straight sperm duct and a crescent-shaped embolus. The shape of the embolus differentiates the species from the related Neaetha absheronica, Neaetha membrosa and Neaetha tomkovichi.

The female has a similar carapace, although smaller at 0.86 mm long and 0.74 mm wide. The carapace is brown and has black areas near the eyes like the male but is covered in brown as well as white scales. White scales can also be found on the brown clypeus, which has longer bristles as well. The sternum and chelicerae are light brown and brown respectively like the male but the labium is darker. The legs are slightly lighter than the male. The abdomen is more clearly different, as it is both smaller, measuring 0.97 mm in length and between 0.72 mm in width, and has a pattern of darker spots on a yellow background. The spinnerets also differ, being light brown.

The females of the genus are generally hard to distinguish. However, the copulatory organs on Neaetha wesolowskae are distinctive. The epigyne is large with a characteristic central pocket. This species has distinctive ovoid, rather than crescent-shaped, copulatory openings that lead to very short copulatory ducts. The spermathecae, or receptacles, are as long as they are wide and sclerotized. The spider is particular similar to Neaetha tomkovichi, differing in the having a larger pocket on the epigyne and the way that the spermathecae are separated rather than together.

Distribution and habitat
The species is endemic to Thailand. The male holotype of the species was found in the Kanchanaburi province in 1979. The female paratype was found in Chonburi province during the same year. This is the most easterly that the genus has been observed. The species lives in rainforests.