Coelopa pilipes

Appearance

In general, seaweed flies are dark-colored, small or medium-sized flies with hairs or bristles. Darker color makes the adults more distinguishable from other species, but larvae are less easily identified. Adults have small eyes and short antennae and legs, and their bodies tend to be more flattened than other species.

Environment, genetic factors, and nutrition contribute to variable measurements such as wing size. In order to adapt to wet seaside environments, ''C. pilipes'' larvae have hair on their posterior parts and spines on their ventral surfaces, as seen in many species that dwell in damp seaweed.

''Coelopa pilipes'' are phylogenetically distant from other species in the ''Coelopa'' genus and thus display certain behaviors that differ from other ''Coelopa'' flies.

Distribution

''Coelopa pilipes'' can be found in European countries with shorelines, such as Belgium, Britain, Denmark, France, Germany, Iceland, Ireland, Norway, and Poland. Other reported locations for ''C. pilipes'' residence include North Africa and Australia, where it is not native.

Habitat

On beaches, ''C. pilipes'' is able to thrive within decaying seaweed, which provides a relatively warm and humid environment throughout the year. Piles of seaweed on beaches are especially common after storms and high tides in the spring, both of which are becoming more severe with climate change. Even when the beach is covered in snow and ice, decay of the seaweed can generate temperatures of 40 °C in the inner layers of seaweed where ''Coelopa'' larvae live.: 451 Exposure to certain seaweed such as ''Fucus'' has been shown to increase mortality of some kelp fly species; however, virgin ''C. pilipes'' are able to delay this effect.

Reproduction

''C. pilipes'' are especially prevalent in European beaches. Year-round, these flies live in washed-up kelp on wrack zones of beaches before adulthood and consume the decaying kelp, mostly of the genera ''Laminaria'' and ''Fucus'' that have a great impact on the flies' survival. Female flies lay eggs in the decaying seaweed, and larvae mature in the warm, moist environment it provides. ''C. pilipes'' has significant sympatry with ''C. frigida''; the two flies are often studied together due to their overlapping habitats and distribution.

Food

Larvae of ''C. pilipes'' feed on the same decomposing seaweed their eggs are deposited on. They may also consume bacteria found on the surface of the seaweed. If only raised on ''Laminaria'' seaweed, the flies have reduced growth due to a lower nutritious value of seaweed. The ''Fucus'' seaweed that the flies prefer most is prevalent in the North Pacific. The presence of ''Fucus'' can be associated with the number of ''C. pilipes'' flies at a certain site.

Evolution

During the summer, populations of ''C. pilipes'' decrease in number. They are most abundant in the fall and winter, when seaweed is most likely to be washed on the beach. All larval instars remain in the seaweed,: 451  and larval aggregations tend to not be mixed in species. If seaweed is washed back to sea, the larval population can decrease significantly with the loss of the seaweed habitat. Pupation begins in drier portions of seaweed, and the development time for ''C. pilipes'' is significantly longer than that of other ''Coelopa'' species such as ''C. frigida''. Adult ''Coelopa'' flies are estimated to live around 2–4 weeks, with some variation.