Female macropterous. Body and legs brown; antennal segment III paler at base than at apex, IV–IX brown; forewing shaded, basal quarter paler, base of clavus dark.
Head with postocular region apparently shorter than eye length; distal maxillary palp segment subdivided. Antennae 9-segmented, III with sensorium not curving around apex, extending to basal half of segment, without internal markings. Mesonotum with 2 pairs of accessory setae medially. Metanotal reticles elongate, without internal markings. Abdominal tergite I almost without sculpture; trichobothria on X nearly twice the diameter of the base of major setae on X. Sternites III–VI with 4 pairs of marginal setae but the lateral pairs arise sub-marginally; VII with only 3 pairs of marginal setae, about 6 pairs of discal setae laterally to sub-medially.
Male not known.
The genus Desmothrips is known only from Australia, with 18 described species (Pereyra & Mound, 2010). D. mendozai is known only from a few damaged specimens. It is another of the species with the forewings largely fuscous but paler in the basal quarter. The sensorium on antennal segment III is not curved around the apex of this segment, and the median metanotal reticulations are slightly elongate and lack internal markings.
Known only from Australia
Known only from three specimens taken at Mundaring, near Perth in Western Australia.