It is not the adult stage of the Harvest
mite which causes the problems, but the six-legged larval stage which
can send people and animals crazy scratching which then leads on to
secondary infection. These are white to orange red in colour, that is
before they have a good feed on you...and very small something like
1/100 of an inch, just about visible. To understand what is going on
we need to know a bit of biology:
Adult harvest mite overwinter near or slightly below the soil and in
other protected places. Females become active in the spring and lay
up to 15 eggs per day in vegetation when soil temperatures are 60°F.
The larvae congregate in groups on small clods of earth, in matted vegetation
and even on low bushes and plants, where they have more access to a
prospective host. The first active stage in the life of the harvest
mite is the six-legged larva and this is the only stage to attack warm-blooded
animals. A drawing (courtesy of Ohio State University) shows the difference
between the adult and the larvae.
life cycle is about 50 to 70 days, with adult females living up to one
year and producing offspring during this time. Multiple generations
occur in warmer climates, whereas only two to three develop each season
in some northern areas/countries. They are active only during the day
and their movements appear to be controlled chiefly by the weather,
aren't we all, they are most active when it is dry and
sunny and least active when the day is cold and wet, as is the case
with most insects. When the larvae come into contact with any warm-blooded
animal (dogs are particularly susceptible), they swarm onto it and wander
in search of a place to attach themselves. Infestation in human beings
generally occurs by way of the ankles when walking in areas where the
mite is common; sitting or lying on infested ground offers even better
opportunities to the mite.
thickness of the skin is probably the most important factor because
the harvest mite feeds by thrusting its small hooked chelicerae (fangs)
into the surface layers of the skin. Where the skin is unusually thick
they attach with difficulty and may be brushed off by the movements
of the host. Young harvest mite larvae attach themselves to the skin
of people, domestic animals, wild animals (including reptiles), poultry
and birds. The preferred feeding locations on people are parts of the
body where clothing fits tightly over the skin such as around the belt
line, waistline, under girdles and under socks, or where the flesh is
thin, tender or wrinkled such as the ankles, in the armpits, back of
the knees, in front of the elbow, or in the groin, especially around
hair follicles (see below again courtesy of Ohio State).
insertion of the small fangs into the skin is painless, and is merely
intended to puncture the skin so that the feeding process can begin.
Harvest mite larvae do not burrow into the skin, nor suck blood.
They pierce the skin and inject into the host a salivary secretion containing
powerful, digestive enzymes that break down skin cells that are ingested
(tissues become liquefied and sucked up). Also, this digestive fluid
causes surrounding tissues to harden, forming a straw-like feeding tube
of hardened flesh (stylostome) from which further, partially-digested
skin cells may be sucked out. After a larva is fully fed in four days,
it drops from the host, leaving a red welt with a white, hard central
area on the skin that itches severely and may later develop into dermatitis.
Any welts, swelling, itching, or fever will usually develop three to
six hours after exposure and may continue a week or longer. If nothing
is done to relieve itching, symptoms may continue a week or more. Scratching
a bite may break the skin, resulting in secondary infections. However,
harvest mites are not known to transmit any disease in this country.
the larva has finished feeding it drops to the ground to complete its
lifecycle. It descends into the soil and, after a period of five or
six weeks, changes into an eight-legged nymph. This stage is sexually
immature like the larva, but it resembles far more closely the adult
male or female into which it eventually develops. Both the nymph and
the adult live in the soil and feed on plant juices or small insects.
They are never parasitic. They prefer moist conditions (as do all mites
as otherwise they would desiccate) and are especially numerous in the
vicinity of rabbit warrens. Thus the lifecycle of the harvest mite is
completed. The eggs laid by the adult in the spring and summer hatch
into the six-legged harvest mites which are most abundant in late summer
and autumn. These, after they have fed on warm-blooded animals, develop
through the nymph stage to the adult.
The harvest mite is
widely distributed in the British Isles and is particularly abundant
on chalk downs. The geological origin of the soil and the climate does
not affect its abundance. Heavy infestations, however, are often found
to be sharply localised; a heavy infestation may occur in the gardens
of one or two houses in a village which is otherwise free from the pest.
They may also be found in town gardens and parks.
Very common around blackberry bushes, woods, fields. Never sit on a freshly used brush hog! My butt was completely covered. I used a rag with bleach on it to scrub with. Killed them all instantly and never itched again!
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After returning from
a chigger/harvest mite-infested area, launder the field clothes in soapy,
hot water (125°F.) for about half an hour (this applies to any insect
infestation, washing clothes on cool wash does not work, so if your
Amani jacket....well you know). Infested clothes should not be worn
again until they are properly laundered and/or exposed to hot sunshine.
Unlaundered clothes or those laundered in cool water will contain the
biting chiggers to again reinfest your skin. As soon as possible, take
a good hot bath or shower and soap repeatedly. The chiggers may be dislodged,
but you will still have the stylostomes, causing the severe itch. Scratching
deep to remove stylostomes can cause secondary infections. For temporary
relief of itching, apply ointments of benzocaine, hydrocortisone, calamine
lotion, or others recommended by your pharmacist or medical doctor.
Some use Vaseline, cold cream, baby oil, or fingernail polish. (The
sooner the treatment, the better the results.)
Mowing of briars, weeds,
and thick vegetation and close clipping of lawns, to eliminate shade
and moisture, will reduce harvest mite larvae populations, and permit
sunlight and air to circulate freely. Harvest mite larvae can penetrate
many types of clothing, but high boots and trousers of tightly woven
fabric tucked into stockings or boots help deter them.
Before going into an
area where harvest mite larvae may be present, protect yourself by using
a repellent or permethrin available at many chemists or hardware stores.
Deet-based repellents are effective for only a few hours, whereas permethrin-based
repellents are for use only on clothing and effective for several days.
Apply the repellent to both the skin and clothing, especially on hands,
arms, or legs, if uncovered, and to clothing openings at cuffs, neck,
waistband, and upper edges of socks. Follow label directions since repellents
may damage plastics, nail polish, and painted or varnished surfaces.
Do not use indiscriminately as severe human allergies can develop. Keep
moving since the worst harvest mite infestations occur when sitting
or laying down in a sunny spot at midday with temperatures above 60°F.
If possible, stick to roads and trails.
Treating known harvest
mite larvae trouble spots is quicker and less expensive than treating
an entire area. Place six-inch squares of black cardboard (black is
a heat sink and will become warmer than the surrounding grass) on edge
in the grass and observe for a few minutes (obviously on a dry day....!).
Any small, yellowish or pinkish harvest mite larvae present will climb
rapidly to the top of the square and congregate there. Make tests in
10 to 12 different spots such as grass, dead leaves, briars, weeds,
etc. Unless the entire area is infested, treat only the spots where
control is desired such as grass around picnic tables, lawn chairs,
or recreational equipment (Always remember, when you are spraying
insecticide none target species are also at risk...poor old ladybirds).
Harvest mite larvae tend to concentrate in "mite islands" while nearby
spots are free of them. They become rather inactive at temperatures
I am not going to make
a recommendations on which insecticide that you can use. Those preparations
that pest controllers and farmers use are not normally available to
the general public in this country (Gt. Britain). I would also not advise
to go getting too much information from American sites on treatments
as the laws on pesticides are different to ours.
Do not wear dog or cat
flea collars on your ankles or cattle ear tags on your shoes to ward
off harvest mite larvae. It is very dangerous resulting in chemical
skin burns and toxic effect to the wearers.
consult your doctor as far as any personal treatment is concerned.