VCSU Macro-Invertabrate Lab
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Order Coleoptera - The Beetles
Staphylinidae-body Dytiscidae-body Elimidae-body
The Coleoptera, or Beetles, are the most numerous, in terms of species, group of animals on this planet. They are a diverse and interesting Order with many families that are aquatic. In North Dakota we have several families that have both aquatic larvae and adults and so we have separate Family lists and keys for both larvae and adults. There are also several Families with only aquatic adults, one Family with only aquatic larvae, and some families for which we haven't collected the larvae. Because of this you will notice that the Families listed in the Adult and Larvae lists are not identical.

General Life cycle - Beetles under go complete metamorphosis. This means they have distinct egg, larval, pupal, and adult stages. The larvae and adult bear no resemblance to each other and so, as in many aquatic insect groups, there are many species in which the larvae and adult have not been associated and described. Interestingly, in groups with aquatic larvae and adults, the intervening pupal stage is terrestrial. When the aquatic larvae is ready to pupate and undergo metamorphosis into an adult, it will crawl onto shore and either burrow into the soil or find a protective area to pupate. When the adult emerges it will reenter the water.

Identification - Adult beetles are characterized by the hard outer covering, called elytra, that covers their backs. The elytra are actually the front pair of wings which have been modified into protective plates. Adults beetles have chewing mouthparts and six distinct legs. Adult identification often involves structures of the mouth, pronotum, elytra, and legs. Larval beetles are very diverse from one group to the next. Some are elongate with gills, others are caterpillar like - although all have distinct segmented legs.

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