Swimming Weevils at British Camp Reservoir, Malvern

By Don Goddard

As part of the Worcestershire County Councils Aqua Vitae project organised by Will Watson I was asked to do a rapid survey of the aquatic invertebrates of British camp Reservoir at Little Malvern at the southern end of the Malvern Hills 350 metres to the east of Herefordshire Beacon where the impressive Iron Age Hill-fort of British Camp is located. This site is administered by Severn Trent is one of the few mesotrophic/oligotrophic water bodies in Worcestershire.

Most water bodies of this sort have a fairly limited but often specialised fauna. A small range of common and local aquatic invertebrates were noted with nothing to arouse excitement until I observed a number of weevils swimming in the collecting tray, not floundering as terrestrial weevils would but swimming like Olympic champions. Upon examination with the microscope there turned out to be two species, Eubrychius velutus (Beck) and Litodactylus leucogaster (Marsham). Both weevils were found amongst the water milfoil, which occurred all around the Reservoir and extended down into deep water. The former species, Eubrychius, was present in large numbers with occasional specimens of Litodactylus mixed with it. This appears to be the only county site for both of these species. As very few Litodactylus were found I am wondering if the main population occurred at a greater depth beyond the reach of the net. I shall have to return with scuba equipment!

Eubrychius velutus (Beck) (Nationally Scarce Category B)

A small rounded weevil associated with water milfoil Myriophyllum sp. It can tolerate brackish water. On the Continent this species has been recorded from spiked water-milfoil M. spicatum and whorled water-milfoil M. verticullatum. The larvae form a cocoon on the food-plant. The adults require well-oxygenated water and are excellent swimmers. They can dive to considerable depths and can withstand a pressure of 20 atmospheres!! (Morris pers. comm.). Adults have been recorded from April to June and from August to September. Widespread but very local in England, also recorded from parts of Wales and Scotland. Threatened by pollution, pesticides and herbicides, eutrophication and habitat loss due to falling water tables, in-filling of pools and natural succession.

Litodactylus leucogaster (Marsham) (Nationally Scarce Category B)

A small rounded weevil associated with water milfoil, Myriophyllum sp, in pools and ditches. It can tolerate brackish water. On the Continent this species has been recorded from spiked water-milfoil M. spicatum and whorled water-milfoil M. verticullatum. Adults have been recorded from March to June and from August to October. Widespread, but very local throughout Britain. Threatened by pollution, , pesticides and herbicides, eutrophication and habitat loss due to falling water tables, infilling of pools and natural succession.

Reference

Hyman, P. S. 1992: A review of the scarce and threatened Coleoptera of Great Britain. (Part 1) Joint Nature Conservation Committee, Peterborough

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