Subject: Giant Red Velvet Mite 


I wrote at the time that the mite was a member of the family Trombidiidae
(suborder Prostigmata) and perhaps a species of _Dinothrombium_.

Recently I came across a couple of old references to this mite which may
be of interest to others:

Annandale, N. 1906. Notes on the fauna of a desert tract in southern
  India. Part II.-Insects and arachnids. Memoirs of the Asiatic Society
  of Bengal, 1(10): 203-219, pl. XI.
Hill, E. G. 1905. The composition of the oil from bir bahoti or the
  "rains insect", (Trombidium grandissimum). Journal of the Asiatic
  Society of Bengal, New Series, 1(3): 74-80.

Hill writes:

"The animal known to natives as _bir bahoti_ and which is described as
the "rains insect", the "red velvet insect", the "lady cow", in the
Cyclopedia of India, and as _Bucella carniola_ in Platts' dictionary, is
a red mite about half an inch long and from a quarter to three-eighths
of an inch in its widest part. It is covered with a scarlet, velvety
down, and appears on the ground at the beginning of the rainy season.
It is only to be found for a few weeks in the year, but it has a great
reputation among the Mahomedans as an aphrodisiac, so it is collected
and kept for sale in the bazaar. The insects from which the author
extracted the oil for his experiments were purchased from a dealer in
Allahabad city. They had been kept for several months, but had not
putrified at all. On pressure they exuded a deep red oil. It is this
oil which is used medically as an external application. The Cyclopedia
quoted above states that the oil is used as a counter-irritant, but it
appears to have no such properties, and its efficacy as a medicine is
probably purely imaginary and due to its colour."

Under the same name _Trombidium grandissimum_ (Koch), Annandale gives
an interesting account of presumably the same species (1906: 216-217 &
figs. 4, 4a). He says it is found in all parts of India where the soil
is sandy and reports on specimens collected at Ramanad and Pamben.
Annandale says the oil which fills the body cavity of these mites (and
which is used as a drug in Northern India) is yellowish, the red colour
reported by Hill possibly being the result of contamination with the
scarlet integumentary pigment. This oil seems to function as a hydrostatic
skeleton in enabling the mite to burrow into the soil, rather like an
earthworm or bivalve mollusc, where the part contacting the soil first is
made slim to facilitate insertion and then anchored by making it fat, with
muscles pulling the body walls inward working against the pressure of the
fluid. Annandale notes that ants, spiders and even a bird (a Jerdon's
Chloropsis) avoided the mites. Presumably the red colour of the mite is
aposematic.

Related species of 'giant red velvet mites' are known from most tropical
and subtropical parts of the world. Here in the USA several species are
recorded, mainly from Arizona and California. According to Newell & Tevis
(1960) these mites are specialised predators of termites during their
adult stage but as larvae are ectoparasites of insects, apparently mainly
of grasshoppers. The classification and nomenclature of these mites
seems to be in a state of flux. Although Hill and Annandale used the
name _Trombidium grandissimum_ for the Indian species, the monograph
of Thor & Willmann (1947) gives it as a South African species, under the
name _Dinothrombium grandissimum_ (C. L. Koch, 1842). In fact, none of the
29 species of _Dinothrombium_ listed by Thor & Willmann seem to be Asian.
A work that may provide more information on the taxonomy of these mites is
that of Southcott (1986), but I have not seen it.

Several specimens of these 'giant red velvet mites' were collected by me
in Sri Lanka, in a more or less open area between scrub forest, close to
the Istripura Cavern, near the village of Serasuntenna, off Pannala, 6-10
November 1984. The specimens are now in the collection of the Department
of National Museums, Colombo.

Newell, I. M. & Tevis, L., Jr. 1960. Angelothrombium pandorae n. g.,
  n. sp. (Acari, Trombidiidae) and notes on the biology of the giant red
  velvet mites. Annals of the Entomological Society of America, 53(3):
  293-304.
Southcott, R. V. 1986. Studies on the taxonomy and biology of the
  subfamily Trombidiinae (Acarina: Trombidiidae) with a critical revision
  of the genera. Australian Journal of Zoology, Supplement Series, 123:
  1-116. [NOT SEEN]
Thor, S. & Willmann, C. 1947. Acarina 3. Das Tierreich 71b: 187-541.