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Extension Entomology

Warehouse Beetle (and Khapra Beetle)

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Article author: Mike Merchant
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Khapra beetle, Warehouse Beetle

Description

The warehouse beetle, Trogoderma variabile, is one of several species of beetle in the genus Trogoderma that are considered pests of stored products. It is the most common Trogoderma pest in homes. The warehouse beetle is oblong to oval, 1/8 to 3/16 inch long, with a dark and light mottled pattern on their wing covers. Adult Trogoderma are fairly short-lived and rarely feed on stored products. However, they are considered excellent fliers and can disperse quite easily.

Warehouse beetle immatures are cigar-shaped and hairy.  Trogoderma larvae have hastisetae, which appear as darker or longer clumps of hairs, and arise directly from the tops of the plates on the last three abdominal segments. These hastisetae can cause gastrointestinal problems if ingested by humans.

It should be noted that the warehouse beetle is a close relative of a highly destructive and tightly quarantined pest called the Khapra beetle Trogoderma granarium. Khapra beetle also known as cabinet beetle is considered one of the 100 worst invasive species in the world.  Because of their warm climates, the Khapra beetle has the most potential for establishment in Arizona, California, Kansas, New Mexico, Oklahoma and Texas. The Khapra beetle is a destructive pest of stored grain and other dried plant—as well as animal—products. It is able to survive almost anywhere in storage facilities that are protected from cold environments. This pest is known for its “dirty eating” behavior; by feeding only a little on each grain, one tiny beetle can damage a surprising amount of stored product.  If you suspect you have a Khapra beetle you MUST contact the United States Department of Agriculture, Animal and Plant Health Inspection Service in your area.

Origin and Distribution

This beetle feeds on a wide variety of foods including cereals, candy, cocoa, cookies, corn, corn meal, fish meal, pets foods, flour, nets, dried peas and beans, potato chips, pastas, spices, dead animals and dead insects.  The warehouse beetle occurs throughout the United States and is common in seaports throughout the world.

Habitat & Hosts

When food becomes scarce or disappears, Trogoderma larvae may enter a lengthy period of inactivity known as diapause, where insects are completely inactive and do not feed. When larvae break diapause, they can resume infesting food items. This ability to diapause in the absence of food combined with the ability to chew through packaging can make control of Trogoderma beetles difficult.

Life Cycle

Females lay around 90 eggs in a lifetime, and the resulting offspring go through a life cycle that takes anywhere from two to four months to complete. In cases of food shortages or poor environmental conditions, warehouse beetle larvae can slow their development by molting numerous times before deciding to pupate.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Warehouse beetles are among the most difficult indoor pests to control because of their ability to find food in obscure places and to disperse widely throughout a building. Successful control depends on a combination of sanitation and exclusion. If exclusion and sanitation are successful, insecticide treatments aren’t required.

When warehouse beetles threaten products in commercial warehouses or storage areas, a monitoring program using sticky traps baited with an appropriate pheromone  is recommended. Sticky traps can also be used in homes where infestations are serious. Traps placed throughout a building can show where beetles are coming from; the traps are also useful for monitoring the effectiveness of control practices. Check traps once or twice a week. You can also use pheromone traps to augment other control methods if you use them to attract adult males in small confined areas. Sticky traps are also available without a pheromone; you can place these traps on windowsills to trap adults that fly to windows.

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Cigarette and Drugstore Beetle

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Article author: Mike Merchant
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Cigarette Beetle, Drugstore Beetle

Description

Cigarette and drugstore beetles are often confused with one another. Adult beetles are rounded in profile, oval shaped, light-brown color, 1/16-1/8 inch-long. A hood-like shield (prothorax) encloses and conceals the head when viewed from above. The femora of each hind leg retracts into a groove in hind coxa. These beetles can be distinguished by the grooving on the wing covers and by their antennal shape. The drugstore beetle’s wing covers possess distinct striae, or grooves, and its antennae are clubbed with three elongated and broadened segments at the tips. The wing covers of cigarette beetles are very smooth, without distinct grooves; and the antennal segments are sawlike, or serrate.

Drugstore beetles are 1/16 to 1/8 inch long. they are brown, and their elytra have distinct rows of pits.  Their antennae end with a loose, three-segmented club. Compared to the cigarette beetle the body is thinner and pronotum is more pronounced.

Cigarette beetles are 1/16 to 1/8 inch long and brown, the elytra is smooth with no grooves. When viewed from the side the angle at which the pronotum borders the elytra gives this beetle a humpbacked appearance. The antennal segments are serrate.

Origin and Distribution

These two species are among the most common stored product pests in Texas homes. They feed on all kinds of plant material including tobacco, seeds, grain, nuts, beans, spices, cottonseed meal, dried fruits and vegetables, flour, spices, and dried herbarium specimens. Animal products such as dead insects, dried fish and fish meal, and leather may also be attacked. On grains, these insects are classified as external feeders. Adults and larvae feed primarily on the outside of the grain, though they may also chew through the outer coat and devour the insides. Both species are among the most common stored product pests both in homes and in commercial food processing and distribution facilities, worldwide. Neither of these beetles bite.

Habitat & Hosts

Both of these beetles are attracted to light and are external feeders.  However, their larvae will stay close to a food source and they do not fly until they reach adult stage.

Life Cycle

Females lay up to 100 eggs over a 6-20 day period in crevices, folds, or depressions in their food. The time needed to develop depends on the food source and other environmental conditions, but ranges from 26 to over 100 days (commonly, 30-50 days). Optimal conditions for development are 70-80% RH, and temperatures between 68° and 86°F. Development generally ceases below 59°F and above 94°F.

The number of larval instars ranges from four to six. Newly hatched larvae are very active and can enter food packaging through very small holes, including minute seams around lids of spice containers. Pupation occurs in loosely constructed pupal cells within the food source. Adults of both species can fly.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

The keys to managing an infestation of cigarette or drugstore beetles include good sanitation, early detection and locating and destroying infested materials.  Insecticides alone are rarely effective. Check all stored food packages and potential food items listed above, and discard any infested food products that you find. Other places to look:

  • Pet foods are common sources of infestation. In addition to checking product bags, look in difficult to clean areas, where pet food or bird seed may have spilled.
  • Old school art projects involving beans, nuts or seeds
  • Forgotten bags of pecans, other nuts
  • Spices, potpourri, other dried plant material
  • Cigarettes, pipe tobacco
  • If your home has been previously infested with a mouse or rat, old rodent nests can be infested. Rodents often hoard food, such as seed or dog food, in their nests. After the rodents leave or are controlled, the food in abandoned nests can be the source of a difficult-to-locate infestation.
  • Rodent bait.  Bait packets thrown in corners of attic or crawl space can be a source years after placement.

Heat treatment is routinely employed against these and other insect pests in museums when receiving new artifacts, like herbarium specimens. Heating artifacts to 125°F for two to four hours, or freezing infested materials at 0°F for six days, is generally sufficient to kill all life stages of anobiid beetles. Small quantities of pet food may be dis-infested by placing in a cold freezer for two weeks. Pet food treated in this manner can then be safely fed to pets.

Dried flower arrangements can be protected to some extent by treating storage containers with a desiccant dust like silica aerogel or diatomaceous earth. Dust the box or container lightly before placing the flowers inside.

Pheromone traps have been developed for both species. These traps use a special sex-scent to attract male beetles. Effectiveness of these traps can be enhanced by placing them near windows or other light sources. In commercial operations pheromone traps can be used to determine where infestations are located and when aerosol applications of pesticides may be needed. Aerosol applications of insecticides like pyrethrins or resmethrin can suppress adult cigarette beetle populations temporarily, but do not eliminate larval infestations.

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Rice Weevil and Maize Weevil

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Article author: Janet Hurley, Bradleigh S. Vinson
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Maize weevil, Rice Weevil

Description

Rice weevils and maize weevils are about 1/8 inch long and brown. They have densely spaced pits on the pronotum that are round (maize weevil) or elongated (rice weevil).  The two species look almost identical without magnification.  Both are internal feeders, which means the larva develops inside whole grain kernels.  Mating often occurs within 24 hours of adult emergence from grain kernels.  this weevil has well developed wings and is considered a strong flier.  This ability allows them to travel from field to storage facilities.  Inside warehouses they can fly great distances to infest food products.

Origin and Distribution

Rice and maize weevils are usually found in grain storage facilities or processing plants, infesting wheat, oats, rye, barley, rice, and corn. Although not often found in the home, they are sometimes found infesting beans, birdseed, sunflower seeds, dried corn, and too a lesser degree macaroni and spaghetti. These weevils do not bite, nor do they damage wood or furniture.

Habitat & Hosts

These insects have chewing mouthparts. They can be in stored grains of all types including wheat, corn, oats, barley, sorghum, macaroni, and other grain products. They may also infest grain in the field. Larvae hollow out kernels of grain and usually attack whole kernels. Holes in the side of the grain are made by adults and by the emerging adults. They build up in numbers in stored grain.

Life Cycle

Females can lay 300 to 400 eggs typically one per cavity. Larvae develop through several stages (instars) inside the grain kernels and also pupate inside the kernel. They may complete a generation in a month in warm conditions. Adults often live for 7 to 8 months and some records are over 2 years.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Monitoring using sticky traps, pitfall traps, or pheromone traps will help with proper identification. In the home, control of these insects involves inspection and removal of infested food products, discarding the heavily infested material, re-packaging material in new containers, and vacuuming kitchen cabinets. Products that need to be retained may be placed in the freezer for several weeks to kill adults and larvae. However, in most cases if it’s not fit for consumption the materials should be disposed of.  In larger infestations of stored grain warehouses and silos, remediation will require emptying the infested areas, cleaning and the use of residual insecticide.

Related Publications

http://agrilifelearn.tamu.edu/Pantry-and-Fabric-Pests-in-the-Home-p/e-486.htm

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Rover Ant

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Article author: Mike Merchant, Robert Puckett
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Rover Ant

Description

Rover worker ants are small (about 1/16″), uniform in size (monomorphic), and vary in color from black, dark brown, to pale blonde. They have 9-segmented antennae without a club, a 1-segmented petiole which is hidden under the abdomen and they do not possess a stinger. The thorax is uneven in shape and the front portion is humped.

Origin and Distribution

Rover ants were rarely considered as a nuisance pest ant. However, since 2015 in Texas, this ant has become more and more prevalent throughout the state. Pest Management Professionals are reporting increased incidents of rover ants inside of structures. These ants are of little economic and medical importance because they do not bite or sting. However, they can be a nuisance in areas where ants are not tolerable, particularly indoors, and can be hard to eliminate.

Habitat & Hosts

Colonies are small ranging in from hundreds to a few thousands members. They contain only one queen per colony. Colonies are usually found in the soil or rotting wood but they will nest in potted plants, wall voids and other harborages. Colonies are commonly associated with soil dwelling aphids and mealy bugs that produce honey dew, a sugary liquid extracted from plants on which these sucking insects feed.

Colonies are formed by mating flights of winged male and female individuals. These flights usually occur in the evening during summer months and winged sexual (alates) are attracted to lights.

Two species are positively identified in Texas, B. depilis and B. obscurior. It is widespread throughout the state and B. obscurior is known to be in the southern portion of the state. It is thought that there may be a third species that has recently been brought to Texas. The population and distribution of Brachymyrmex ants in Texas is expanding.

Life Cycle

Egg, larva, pupa and adult.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Non-chemical or cultural controls should be considered for controlling these ants first. Infestations are often associated with moisture and or fungal decay. Correction of moisture problems will help with control. Any wood that is severely damaged due to water should be replaced. Around the home, remove or treat nesting areas under landscape timbers or rocks.

Rover ants have proven to be one of the more difficult ants to control. They seem to be not attracted to many liquid or granular ant bait formulations. Find entry points on exterior of structure and seal if possible and/or treat with a contact insecticide. Gel baits and dusts may be used in electrical sockets for indoor control. If ants are in a void area, an aerosol may be used. Always follow all pesticide label directions.

Related Publications

Rover Ants, Urban and Structural Entomology Program at Texas A&M University.

Odorous House Ant

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Article author: Bradleigh S. Vinson
Most recently reviewed by: Pat Porter (1970)

Common Name(s): odorous house ant

Description

Workers are one size, about 1/8 inch – 3/16 inch and black to brown. The waist (pedicel) has one segment with a flattened node that is difficult to see. These ants emit a disagreeable, rotten coconut-like odor when crushed. The tip of the abdomen lacks a circle of hairs.

Photo of odorous house ant.

Odorous house ant. Photo: Bart Drees.

Origin and Distribution

Odorous house ants are very fast moving and run erratically. They form foraging trails to food sources. They do not sting. They are cavity nesters, preferring to nest in soil sometimes under stones, boards, or in hollow twigs.  Indoors they can nest in wall voids or under floors.

Odorous house ants have moderate sized colonies of two to five thousand individuals. Although most feed primarily on honeydew and tend honeydew excreting insects in nature, many scavenge and are attracted to sweets and meat products.

 

Habitat & Hosts

Indoors, nests are found inside wall voids, around heaters and hot water pipes and in crevices around sinks and cupboards. Outdoors, nests are shallow, often under objects such as rocks, landscape timbers and mulch. They prefer sweets but will eat food with high protein (meat or carrion). These ants are fond of honeydew and tend honeydew-producing insects.

Life Cycle

Egg, larva, pupa and adult.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

The most effective control method is with ant bait products.

Related Publications

Identifying Household Ants. Mike Merchant, Texas A&M AgriLife Extension.

Managing Household Ant Pests.

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