common names: Guano Beetle, Lesser Mealworm
scientific name: Order Coleoptera, family Tenebrionidae, Alphitobius diaperinus; family Dermestidae, Dermestes carnivora.
size: Adult--1/4" to 3/8", larva--3/8" to 5/8"
identification: Alphitobius spp.--corrugated wing covers on the adult beetles, wireworm-looking larvae. Dermestes spp.--beetles have slight wing covers with some coloration, larvae look like fuzzy lady beetle larvae.
biology and life cycle: Complete metamorphosis.
habitat: Bat caves.
feeding habits: The meat eaters eat dead and sick bats and other animals in caves. The others eat bat droppings. Both foods are digested into a clean, natural fertilizer.
natural enemies: Cave mice, other predator animals, and predator insects.
economic importance: Keep bat caves more sanitary; very beneficial insects.
natural control: None needed.
organic control: None needed.
insight: According by Brian Keeley of Bat Conservation International, Bracken Cave in San Antonio serves as home for one of the densest populations of mammals on the earth. Every spring an estimated 20 million Mexican freetailed bats (Tadarida brasiliensis) return to this cave to raise their young. Scientific studies show that a female freetailed bat that is nursing a pup will consume her weight in insects every night. For 20 million bats that's an estimated 250,000 pounds of insects nightly all summer. Why doesn't the cave fill up with guano?
The number of different insects involved in the biology of the cave is too great to discuss in detail. However, two different beetles, the guano beetle and the dermestid beetle, play a major role in the "processin1/4" of the bat guano.
The guano beetle, also called the lesser mealworm, is the major processor of the guano. The entire life cycle of the guano beetle from adult to egg to larva to pupa stages is carried out in the cave. The larvae look similar to, but smaller than, the mealworms for sale at the pet store. Because of the vast quantity of guano that is available during the summer, the population of the beetles increases dramatically, causing the floor of the cave to look like a seething mass of life.
The dermestid beetle (Dermestes carnivora) also attains very large populations and plays an important role in the processing of the debris collecting on the floor of the cave, but they do not eat the guano. As the scientific name of this species indicates, the larvae of this beetle eat flesh. With that many bats in the same area, some are bound to fall to the floor and die, and these bats are promptly consumed. Researchers entering the cave have to wear special protective clothing to avoid being attacked by the dermestid beetles. A freshly fallen bat can be consumed by the dermestids in minutes.
The combination of these two beetles keeps caves from rapidly filling with the guano and debris that results from this massive population of bats. These beetles serve as the cave janitors. Humans have been taking advantage of the guano for use as fertilizer and, in earlier times, for the manufacture of gunpowder. Thanks to Brian Keeley from Bat Conservation International for this information.