Darkling beetle
| Darkling beetles | |
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| Heliotautus ruficollis | |
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| Family: | Tenebrionidae Latreille, 1802
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Alleculinae | |
Darkling beetles (also known as Darkening beetles) are a family of beetles found worldwide, estimated at more than 20,000 species. Many of the beetles have black elytra. Darkling beetles eat both fresh and decaying vegetation. Major predators include birds, rodents, sun spiders, and lizards. The larval stages of several species are cultured as feeder insects for captive insectivores, and include the very commonly known mealworms (Tenebrio molitor) and superworms (Zophobas morio), and the lesser-known mini mealworms (Tenebrio obscurus).
Some species live in the dry Namib desert and have evolved modifications that help them collect water from the fog that condenses on their elytra.
Raising darkling beetles from larvae through adulthood can be a rewarding biology project for lower school educators.
Characteristics
This family of beetles may be identified by a combination of features, including :
- An 11-segmented antenna which may be filiform, moniliform, or weakly clubbed.
- First abdominal sternite entire and not divided by the hind coxae.
- Eyes notched by a frontal ridge.
- Tarsi have four segments in the hind pair and 5 in the fore and mid legs (5-5-4.) The tarsal claws are simple.
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A Coelometopine from India -
A Platynotine from India -
A Tock-tock from SNamibia
Notable species
Tenebrio molitor is commonly used as food for terrestrial amniotes kept in terraria. Zophobas morio, or Superworm, is another commonly used live food insect among reptile keepers and is notable due to it being slightly larger and containing smaller amounts of chitin than Tenebrio molitor. Tribolium castaneum is a popular laboratory animal and model organism, especially in studies of intragenomic conflict and population ecology studies. These two, along with other Tribolium species (e.g. T. confusum, T. constructor) and Gnathocerus cornutus, are pests of cereal and flour silos and other storage facilities.
In North America, species of the genus Eleodes are known as darkling beetles, particularly the species called the pinacate beetle or desert stink beetle.
Rearing mealworms into adult beetles
Mealworm is a common name used for tenebrionid beetle larva. They are found in stored grain and related products. They vary in size from the very small, newly hatched larvae to final instar larvae that can be up to an inch long.
Mealworms are commonly used as feed for reptiles, fish, and birds and are easy to find from supply companies. They can be grown in a wooden box eight to ten inches deep. They grow best in containers with large surface areas. The sides should be smooth to prevent them from escaping. The mealworms are mostly nocturnal and prefer a dark environment. Some sand may be provided at the bottom.
The food for the larvae can be flour or cereals. The temperature should be even and the box well ventilated. Some moisture can be provided by way of fruits or vegetable matter. The rearing trays are best left undisturbed.
When adults arise from the larval population, another tray should be provided, prepared with the same food mixture as in the first. The adults should be placed in this tray to lay eggs for more young worms. As soon as these young worms have grown sufficiently to be handled they should be put in the first tray and allowed to grow as large as desired. By using a two tray system, one should be able to provide a continuous supply of worms.
External links
- Tenebrionidae.net- information and pictures about darkling beetles
- Alphitobius diaperinus, lesser mealworm on the UF / IFAS Featured Creatures Web site
- Leichenum canaliculatum variegatum, Madagascar beetle on the UF / IFAS Featured Creatures Web site
