''Trombidium grandissimum'', commonly known as the giant red velvet mite, is a species of

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

in the genus ''

Trombidium ''Trombidium'' is a genus of mite with about 30 described species. Species * '' Trombidium auroraense'' Vercammen-Grandjean, Van Driesche & Gyrisco, 1977 – New York * '' Trombidium breei'' Southcott, 1986 – Europe (host: ''Agapetes galathea' ...

'' in the family

Trombidiidae Trombidiidae, also known as red velvet mites, true velvet mites, or rain bugs, are small arachnids (eight-legged arthropods) found in plant litter and are known for their bright red color. While adults are typically in length, some, such as t ...

. The mite is endemic to northern and central India, where it is called 'Badal kida', 'Bhir-buti', 'Birbhoti' or 'Bir Bahoit'. ''T. grandissimum'' is normally seen during the rainy season or after recent rain events, and therefore has the nickname of "rain bug".

Description

''Trombidium grandissimum'' has a soft cushioning skin covered with bright red coloured hairs. These insects are terrestrial and live in soil burrows. They are found in dry, arid, desiccating regions. These mites are predatory in nature and feed on termites and eggs of insects, like ants. They share many similarities with the order Araneae. The insect is used therapeutically in the treatment of paralysis and sexual dysfunction. The mites are a bright red colour attributed to the pigment carotene. A study on the spider mite ''Tetranychus urticae'' shows that carotene is beneficial for their hibernation. ''T. grandissimum,'' belonging to the same order as spider mites, spend an extensive period of time in hibernation under the soil. This might be the reason why they also depend on red pigmentation by which their haemolymph is usually coloured.

Microscopy

The mites were observed under stereo microscope for the detailed classification and analysis of different parts of their body, and structural samples were processed using

ESEM The environmental scanning electron microscope (ESEM) is a scanning electron microscope (SEM) that allows for the option of collecting electron micrographs of specimens that are moisture, wet, scanning electron microscope#Sample preparation, unc ...

and FESEM. The FESEM images of the front leg

sensilla A sensillum (plural ''sensilla'') is an arthropod sensory organ protruding from the cuticle of exoskeleton, or sometimes lying within or beneath it. Sensilla appear as small hairs or pegs over an individual's body. Inside each sensillum there are ...

hairs and claws at the tip usually measured around 500μm. Stalked eyes pointed with white arrows measured around 1mm. White arrows magnified by ESEM were measured around 400μm. The red velvet skin is shown to be covered by sensitive hairs. The whole body hairs showing the branches and arrangement measured around 50μm in size.

Behavior

''Trombidium grandissimum'' were found to be sensitive towards light and they become activated when light was focused on them. In their natural habitat they were found to move on horizontal plane. They seemed to be reluctant to climb up against the gravitational force which may be due to their bulky body size and shorter legs. They can easily wriggle their bodies through small openings and thus can easily get inside the burrows of ants and other insects to feed on their eggs. Males and females of Trombidiidae mites perform encircling dances, after which they pair for mating. A dead mite was found to be surrounded by ants suggesting that they are non-toxic to other species and their cannibalistic nature suggests the same.

References

{{Taxonbar, from=Q115393319 Trombidiidae Endemic fauna of India Animals described in 1867