Various species of carpet beetles (dermestids) are commonly found in homes. While they can appear any time of the year, frequently when the temperature warms up (probably sometime in July, just kidding probably mid-March through April), populations may increase.
Two stages of the carpet beetle are usually seen, adults and larvae (dermestid larva image below). Carpet beetle adults are small (1/16 to 1/8 inch), oval and with variations in color, from solid black to having white or orange markings. The full grown larvae are similar in size to the adults for each species and tend to be cigar-shaped and banded with dark, long hairs. In some species (i.e. the black carpet beetle) the larvae have a tuft of hair at the tail-end of the body which will make them seem larger. Often, only larvae will be seen because the adults feed on pollen and leave the food once they have emerged from their pupal stage. Sometimes only the larval "skins" will be found. Dead adults are often found in window sills because they fly to the light, trying to get outside.
Carpet beetles occur naturally outdoors but will take full advantage of any "offerings" left out by generous humans. These insects scavenge and feed on animal matter like dried meats, dead insects, hides, and woolens, and occasionally severe infestations will be found. The name "carpet beetle" comes from their former importance as a pest of woolen carpeting. They do not feed on carpet made from synthetic fibers. Low-level infestations are of minor importance, and usually occur in the spring when they feed on dead insects in attics and window sills, and then move into dwelling areas when they run out of food. Sometimes the presence of these insects is an indication of dead animals like mice in hidden areas. Essentially nearly every home will harbor these "recyclers" at some time.
Occasionally, severe infestations occur in food products, stuffed animals, woolen fabrics, feathers, and other items of animal origin. The worst infestation I ever saw was when a gentleman was trying to start his own dog treat business out of the basement of his home. He put a dried jerky-like piece of meat in a thin sandwich bag and left several dozen bags in his basement storage room. The carpet beetles quickly found the treats and a big party ensued. The gentleman was alarmed when hundreds of fuzzy worms (the larvae) began appearing upstairs. A quick inspection found the treats riddled with holes. The beetles had easily chewed through the sandwich bags to get to the dried meat. Dogs everywhere mourned.
Usually the solution to carpet beetles is finding the food source and removing it. Insecticides should only be used in addition to a thorough cleanout of potential breeding sites. Most household insecticides will provide some residual effect for control but carpet beetles may re-infest from outdoor sources during the warm season.
Closely related species, such as the warehouse beetle, varied carpet beetle and larder beetle, (image to the right) have expanded their diet and also feed on grain and grain-based products. They are especially common in flour and cereals, but also are found in candy, cocoa, cookies, corn meal, nuts, pasta, dried spices, and many other dry foods. Because some of these species feed on woolens, infestations in the pantry may spread and damage valuable clothing, woolens, and furs. Proper cleaning and storage of natural fabrics will help prevent damage.
A good resource from which some of this article was taken is from Colorado State University.