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Living Organism Care Guide: Bean Beetles

Living Care Information

Callosobrauchus
maculatus

commonly known as cowpea weevil,
cowpea seed beetle

Quick Start Information

  • Your culture of bean beetles will maintain itself for several weeks with little care.

  • Leave the lid on the culture casing unless beetles are needed for an experiment. This limits the potential for escapees.

  • You will need a supply of dried organic beans as a host and food source for the beetles to continue their life cycle. Check the feeding section below for the beetles preferred food options but we use organic mung beans in our labs.

About the Organism

  • An adult female can lay over a hundred eggs on the surface of legumes.
  • During development, bean beetle larvae feed on the interior of the host seed, eating the tissue just under the surface.
  • Adult beetles only live about a week.
  • Bean beetles are a damaging agricultural pest species.
  • Bean beetle colonies can present two morphs, flightless and flying. Ours are sent as a flightless morph.
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Coleoptera
  • Family: Chyrsomelidae
  • Genus: Callosobruchus
  • Species: maculatus

Preparation

It is important to understand that adult bean beetles live only 1-2 weeks. Adult females will mate and lay hundreds of eggs on fresh beans during that time. New adults will emerge after about 20 days depending on temperature. The new adults can be placed in new containers with fresh beans to begin the life cycle again.

Housing

You will receive a culture containing enough beans to maintain itself for several weeks with little care. Leave the lid on the culture unless students need access to beetles to set up experiments.

Feeding

Bean beetles can be provided with dried beans such as mung beans, adzuki beans, black eyed peas or cowpeas to lay their eggs and feed larvae. Adult bean beetles do not require food.

Maintaining and culturing

If you wish to maintain a culture, you will need petri dishes or cups with lids. If using cups, use a pin to punch a few holes in the lids for ventilation. Add enough mung beans to cover the bottom of each container in a single layer. Add at least 1 male and 1 female to each container and put on the lid. Additional information on techniques used to culture bean beetles can be found in our Bean Beetle Study Kit and Experiments with Bean Beetles Book.

Disposal

Dispose of all beetles, beans with eggs, infested beans, and spent beans by placing them in a secure self-sealing bag and freezing for at least 2 weeks. After that, dispose of the unopened bag in the trash. Bean beetles are known agricultural pests and should not be released under any circumstances.

Biosafety

No biosafety information applies for this organism.

Video

No video or video playlist applies for this organism.

FAQs

How large are bean beetles?

Adults have a body length of about 3 mm (1/8˝).

How do I differentiate between male and female bean beetles?

Males and females can be distinguished by coloration on the plate covering the end of the abdomen. In the female, the plate is enlarged and is dark in color on both sides. In the male, the plate is smaller and lacks stripes and dark coloration. Generally, females are larger in size than males.

How long is the life cycle?

Eggs are deposited on the surface of beans and hatch in 5 to 20 days, depending upon ambient temperature. The larva has chewing mouthparts and makes its way into the bean where it feeds and matures. Temperature strongly affects generation time: At room temperature, adults may require 7 weeks for emergence. In an incubator at 30° C, adults may emerge in 3 to 4 weeks. The adult stage is brief, lasting only 10 days to 2 weeks. The adults do not need food.

Is there anything unusual about the life cycle?

There are 2 morphs or body types of the bean beetle: a sedentary morph, which is contained in the cultures we ship, and a dispersal morph. The beetle remains in the sedentary morph as long as it has beans available for infesting and the population does not become too dense. This morph of the beetle seldom flies. At higher population densities, the dispersal morph begins to emerge. As the name implies, this morph tends to fly away or disperse. Most of these dispersing beetles die, but a lucky few may find a new supply of beans to infest, and the sedentary morph will predominate again.

Need help?

We want you to have a good experience. Orders and replacements: 800.334.5551, then select Customer Service. Technical support and questions: caresheets@carolina.com

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