Berosus affinis

This record describes Berosus affinis (species). Recorded family: Hydrophilidae. Recorded order: Coleoptera.

Identification and Appearance

A small (3.5 to 4.5 mm) water beetle. The elytra have a straw ground colour with a prominent pair of dark spots near the suture and additional spots nearer the apex. The black head, bulging eyes and broad dark patch on the pronotum are particularly noticeable. This dark pronotal patch may have a pale central line but this doesn't extend beyond half way. The elytral interstices are flat. Berotus luridus is generally darker so the elytral spots are less noticeable.The dark pronotal patch has a pale median line that extends at least half way down. The elytral interstices (strips between the striae) are raised into ridges (flat in B. affinis ). Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters. Widespread in the southern half of Britain but rather local.

Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Hydrophilidae
Genus: Berosus

Imported taxonomy record. Source availability varies; see the source references and editorial policy below.

Habitat and Range

Habitat

Ponds and other marshy habitat types.

Seasonal Activity

All year round.

Additional species information

Recorded status

Widespread in the southern half of Britain but rather local.

About Primitive Winged Insects: the wider group

Order-level background for Coleoptera, the group containing Berosus affinis. Species-specific details appear above.

Group overview

Coleoptera is the largest order of insects with over 400,000 described species, representing ~25% of all known animal species and ~40% of all insects. In the U.S. alone, nearly 30,000 beetle species have been identified.

Ecological role of the group

Beetles are prominent decomposers, especially in forests, breaking down dead wood and recycling nutrients. As predators, they reduce populations of pest insects. Many species are also important pollinators of flowering plants.

Economic and practical significance of the group

Beetles have major economic significance: leaf beetles (Chrysomelidae) and weevils (Curculionoidea) are among the most destructive agricultural pests globally, costing billions annually, while predatory species like ladybugs provide natural pest control.

Recorded sources for this group: Britannica, Smithsonian, NCSU Entomology. Imported estimates may describe particular regions or reporting periods.

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