It is characterised by its covering in dense white hairs and its preference for living high in the tree canopy of tropical rainforests.

Its copulatory organs are typical for the genus, but the female has a ridge in the middle of its epigyne that helps to distinguish it from other Pachyballus spiders.

Pachyballus caelestis is a species of jumping spider, a member of the family Salticidae, that was first described by the arachnologists Wanda Wesołowska, Galina Azarkina and Konrad Wiśniewski in 2020.

[4] In their 2003 phylogenetic analysis, Wayne Maddison and Marshall Hedin noted that the genus is closely related to Mantisatta, despite the large physiological differences between them, and the similarity of those spiders with a group of genera they termed Marpissoida.

[7] In 2015, Maddison listed the genus within the tribe Ballini, derived from Simon's original name, but attributed to an earlier author, Nathan Banks from 1892.

The carapace, the hard upper part of the cephalothorax, is black with a covering of dense short white hairs.

[3] The spider's copulatory organs are typical for the genus and include a rounded cymbium that partially encloses a smaller bulbous palpal bulb.

The spider's epigyne, or externally visible copulatory organ, is oval with a depression in the middle that is split into two by a short wide ridge.

The two copulatory openings lead to wide ducts and relatively small receptacles, or spermathecae.

Although the looped embolus is unusual, other Pachyballus spiders have similar shapes so distinguishing the species from others in the genus is difficult.

The female has a distinctive ridge in the middle of the epigyne and straight copulatory ducts which aids recognition.