INTRODUCTION
The varied carpet beetle probably gets its common name because there is
great variation in the color pattern on its dorsal surface.
This species is known to cause dermatitis in humans. It is worldwide
in distribution and is found throughout the
United States
.
RECOGNITION
Adults abut 1/16-1/8” (1.8-3.2 mm) long. Body black, with pattern of yellow and white scales on pronotum and elytra (wing covers), 2 transverse
zigzag bands of white scales bordered by yellow scales on elytra; scales elongate, 2-3 times as long as broad; lower/underside of body covered with grayish
yellow scales. Antennae
short, with 3-segmented, compact club. Posterior end of
elytra evenly rounded. Abdominal 5th sternite broadly and
deeply emarginate (notched) apically. In addition, body oval, head more or less concealed
from above, with a median
ocellus, and tarsi
5-5-5
.
Larval
length up to ¼” (4-5 mm). Stout, widest posteriorly. Color dark brown to black. Covered
with brown hairs; with tufts of spear-headed hairs (hastisetae)
arising from membranous areas on the sides of abdominal segments
5-6-7 pointing towards the rear and converging towards the center,
heads of spear-headed hairs of hind tufts equal in length to
combined length of 7-8 preceding segments. Antennae with segment 2 less than 2.5 times as long as broad. Abdominal sternites entirely membraneous.
SIMILAR GROUPS
(1) Carpet beetle (anthrenus schrophulariae) with brick red
scales along midline of elytra (wing covers). (2) Furniture
carpet beetle (Anthrenus flavipes) with pronotum and
elytra patterned with white, yellow, and brown scales, underside
of body pure white, posterior end of elytra with shallow notch
at midline. (3) Other dermestids (Dermestidae) with less compact
antennal club of usually more than 3 segments, hairs on dorsal
surface somewhat flattened but not scalelike, and/or 5th abdominal sternite not deeply notched apically. (4) Poderpost/deathwatch/anobiid
beetles (Anobiidae) with antenna longer, if clubbed, then club
asymmetrical (lopsided). (5) Other beetles with oval body form
lack a median ocellus and/or lack scalelike hairs.
DAMAGE AND SIGNS OF INFESTATION
Fabrics typically have much surface damage and holes
here and there, but larvae can cause large irregular holes in
material. Furs and brushes have mostly the tips of hairs damaged,
leaving uneven areas. With museum insect specimens, the accumulation
of fine powder/frass beneath the specimen is often the only
indication of these beetle’s presence. Larval caste/molt skins
are often present. Frass/droppings are minute, irregular in
form, often the color of the material being damaged. The larvae
may burrow through packaging materials when seeking food.
BIOLOGY
Females do not always lay their eggs on larval food material. The eggs
hatch in 17-18 days. The larval period ranges from 222-323 days
but may last up to 623 days under Adverse conditions of temperature, humidity, and food, and requires
an average of 7-8 molts (range 5-16). The larva pupates in the
last larval skin and pupation lasts 10-13 days. Developmental
time (egg to adult) usually requires 249-354 days at room temperature,
but may take as long as 2-3 years depending on temperature and
food. Adult males live 13-28 days whereas, females live 14-44 days.
One
case of dermatitis occurred in a man over a 5-year period due
to hypersensitivity to an infestation in his bedroom carpet.
Inhalation of large quantities of the larval spear-headed hairs
may cause pulmonary irritation; Anthrenus spp. Are known to cause this condition.
HABITS
Varied carpet
beetle larvae feed on a wide variety of animal and plant products.
Animal-origin materials include woolens, carpets, furs, hides,
feathers, horns, bones, hair, silk, fish meal, insect pupae,
and dead insects. Plant-origin materials include rye meal, corn,
red pepper, cacao, cereals, etc. Their favored foods are insects
and spiders which makes them a major
pest of museum collections and buildings with cluster fly, boxelder
bug, etc. problems.
On
fabrics, larvae tend to surface graze but are quite capable of making small or large irregular
holes. On furs and bristles, they damage mostly the tips leaving
uneven areas. On dead insects, they typically feed from within
and the accumulation of fine powder/frass beneath the specimen
is usually the only indication of their presence. The larvae
may burrow through packaging materials to get to the contained
food.
Adults
are found outside during warm weather. They are often found
on flowers, particularly in the spring and especially on spiraea spp., where they often eat the pollen. Females seek out
the nests of bees, wasps, and spiders as oviposition sites,
as well as bird nests. Inside, adults are often found at windows
during the spring.
The
primary breeding areas are quite diverse and may include obscure
or unusual places such as wall/ceiling voids where yellowjackets,
honey bees, etc. lived or where cluster flies, boxelder bugs,
etc. overwintered, rodent bait left in attics, crawl spaces,
or basements; wasp and hornet nests in attics, under eaves,
around windows, etc.; dead lint and hair accumulate; animal
trophies or rugs; insulation which contains animal hair; dead
animals in the chimney flue; etc. In such places, the larvae
feed on the animal and/or plant material present.
The
larvae tend to wander about and can be found far from the primary
infestation. When disturbed, the larva erect their hair tufts
and spread the bristles and hairs, forming a ball.
Adults
hatching form indoor pupae avoid or shun light until egg laying is mostly complete, and then become attracted to light. Most
outdoor adults show an attraction to light.
CONTROL
The key to controlling varied carpet beetles is to find the primary source(s)
of infestation and eliminate it/them. Besides the obvious clothing,
furs, drapes, carpeting, and stored products, it may be necessary
to check for the more unusual places such as those listed above.
Ask the customer about both current and past occurrences of
flies in the winter, boxelder bugs, rodent problems, birds nesting
on/in the building, etc.
The
thorough inspection should be followed by good sanitation practices,
and pesticide application when required. Museum specimens may
be treated with heat and/or cold if applicable (be careful of
possible damage to specimens) or with fumigants. Refer to the
control section under the general treatment of fabric and paper
pests for details.