In different parts of Europe and America, and especially in the warmer
regions, or in sheltered gardens, shrubberies, and pastures, different
species of the trombidium abound, and the young hexapod larvæ attack man
and beast, burrowing under the cuticle and giving rise to extreme
itching and persistent and irritating rubbing of the affected part.
These parasites belong to the family of acari or mites, so that the
condition they produce is one of acariasis or mange, only the offender
is not a compulsory parasite, but appears to survive in certain soils
and in the vegetation independently of animal hosts. Their parasitism is
therefore accidental and non-essential to their survival.
The trombidian parasite usually found in Europe is the Trombidium
Holosericeum or silky trombidium, so small (in its larval state) that it
is just visible to the naked eye as a bright scarlet point when moving
on a dark background. It was formerly called Leptus Autumnalis and is
familiarly known as the red beast, _bete rouge_, _harvest bug_, etc. The
common American species is of a dull brick red, so that it is less
easily detected even on a dark background. It is familiarly known as the
_jigger_, though quite distinct from the _chigoe_ or burrowing flea of
the West Indies.
The domestic herbivora get these parasites on the nose and lips while
browsing on the pastures and contract an intolerable itching which may
lead to violent rubbing, abrasions and scabby exudations. The skin
becomes thickened, scabby and rigid, and as new accessions are
constantly received the malady continues until cold weather sets in. The
affection is not in any sense dangerous, and the attacks may be warded
off by a daily application of one of the common parasiticides—decoction
of tobacco, tar water, solution of creolin, naphthalin, etc. The mere
seclusion of the infested animal indoors, without green food, will cure,
as the larvæ pass through their parasitic stage in a few days and drop
off.