Whitemarked Spider Beetles

Facts, Identification, & Control

Scientific Name

Ptinus fur

Appearance

What Do They Look Like?

White Marked Spider Beetle
White Marked Spider Beetle image licensed under CC

  • Size: The whitemarked spider beetle adult is about 1/4 inch long. Male specimens are smaller than females.
  • Characteristics: This group of beetles is called spider beetles because adults look a bit like small spiders with long legs and an unusually large, globe-shaped abdomen. However, the shape of the whitemarked spider beetle’s abdomen is more elongated when compared with other members of the spider beetle group.
  • Color: Light brown in color with patches of white hairs on the front and back of the outer wings.
  • Larvae: The larval or grub stage is shaped like a “C” and cream colored with a light brown head. Full-grown larvae are just about the same length as the adults and look somewhat like the larvae of the drugstore beetle.

How Did I Get Whitemarked Spider Beetles?

Most spider beetles need high humidity to survive. For this reason, homeowners find the beetles in damp basements, attics, and crawl spaces. Attics with bird, bat, or rodent infestations are especially vulnerable. Cracks in walls or window wells also allow the insects inside.

These pests feed on stored foods, animal droppings, and dead insects. Whitemarked spider beetles prefer spoiled goods, so residents who do not keep products in airtight containers or in low humidity locations risk infestation. Poorly packaged grocery items may also transport the pests directly into pantries.

How Serious Are Whitemarked Spider Beetles?

When the pests invade a food item, they leave behind both feces and body parts. As a result, whitemarked spider beetle infestations cause the spoilage and waste of expensive goods. These insects also feed at night, making it hard for residents to find problems before the damage occurs. One of the best ways to discover a whitemarked spider beetle infestation is to set out sticky monitoring traps and examine the traps for beetles that are trapped on the monitor’s sticky surface.

How Do I Get Rid of Whitemarked Spider Beetles?

What Orkin Does
Whitemarked spider beetle control, like other stored product pests, depends on sanitation, inspection, and direct control actions. Managing this beetle is very difficult since it feeds on so many different items. For example, adult beetles found in the kitchen pantry may originate from bird or rodent nests, bat droppings in attic spaces, or from dead insects in an exterior or interior wall.

Your pest management professional will offer some important considerations and procedures for both homes and commercial warehouses depending on the specific situation:

  • Sanitation: Remove spilled food daily and clean with a vacuum, especially along walls and edges of cabinets and food storage pallets where spider beetles and food products tend to accumulate. Inspect the interior and exterior of your home or building for the presence of damaged grains and seeds, opened or damaged food containers, dead insects, or bird and rodent nests.
  • Moisture Control: If possible, humidity control equipment should be used to reduce inside moisture.
  • Traps: Use sticky traps to capture beetles. Your pest management professional will provide identification of insects on the traps. Place traps close to where the beetle’s sources of food are located.
  • Food Storage: Store products in containers with tight fitting lids, especially if the contents are not used often. In the warehouse, put infested products inside sealed plastic bags before disposal. This will help lessen the spread of the beetles.
  • Food Inspection & Rotation: Inspect food products you purchase at the store. Organize and rotate food items so that older products are used or shipped out before newer ones. This is important since whitemarked spider beetles move from infested products more and more as the infestation increases.
  • Warehouse Considerations: In a warehouse, inspect salvage areas where broken packages are kept prior to disposal and be sure to keep food storage pallets at least 18 inches from the walls. This makes cleaning and inspection much easier for your staff and your pest management professional.
  • Temperature Extremes: The use of cold and heat is effective to kill adults, larvae, and eggs. Contact your pest management professional for advice and recommendations before using these methods yourself.

Your local Orkin technician is trained to help manage whitemarked spider beetles and similar pests. Since every building or home is different, your Orkin technician will design a unique program for your situation.

Orkin can provide the right solution to keep whitemarked spider beetle in their place…out of your home, or business.


Behavior, Diet, & Habits

The common name spider beetle stems from the insect’s appearance of looking somewhat like a long-legged spider, but in fact they are really beetles.
What Do They eat?
Whitemarked spider beetles are scavengers that feed on damaged or spilled products and organic matter. Preferred foods include:

  • Animal skins and dead insects
  • Beans
  • Cereals
  • Chocolate  and cocoa powder
  • Corn meal
  • Fruits
  • Grains, seeds, and nuts
  • Herbs

Where Do They Live?
In general, the most likely locations for whitemarked spider beetle infestations are homes and commercial food storage or production facilities. They are often found in humid environments and feed on foodstuffs spoiled by dampness. Infestations are commonly found in:

  • Grain elevators
  • Homes
  • Libraries
  • Museums
  • Warehouses

Life Cycle

Whitemarked spider beetles develop by complete metamorphosis and go through four stages:

  1. Egg
  2. Larvae (grub)
  3. Pupae (cocoon)
  4. Adult

Eggs
Females lay individual eggs in cracks and crevices close to the beetle’s food supply. Generally, eggs hatch in about two to three weeks.

Larvae
Larvae go through three instars, taking about two to three months to complete the larval stage. The full-grown larvae spin a silk cocoon web and either go into an extended resting period or pupate immediately.

Pupae
The pupal stage takes about two to three weeks to complete, but adults may remain within the cocoon for a month or more before developing into sexual maturity.

Adults
Upon emergence, adults feed and mate. Whitemarked spider beetle males, but not females, have the ability to fly. Adults may be seen on basement walls in the winter. Depending on temperature and humidity, it takes about four to nine months to complete one generation.