Phaedon tumidulus (Germar, 1824)
Common throughout England, Wales and southern Scotland with only scattered records north of Edinburgh-Glasgow (Cox). Adults are found throughout the year in a wide range of habitats supporting their foodplants. They are common throughout the Watford area in woodland, parkland, wasteland and domestic gardens, during the winter they occur regularly in grass tussock samples and under bark. Adults are active from the first warm days of March and seem to be adventitious, being found whenever low herbage is swept. There is one generation each year, eggs are laid from early spring over a protracted period and full grown larvae are found from May to August. Large groups consisting of adults, sometimes in their hundreds, and larvae in all stages of development may be found on Hogweed across the western part of Cassiobury park throughout the summer, their presence made obvious by the ravaged leaves, both larvae and adults may be seen feeding on the foliage, larvae usually lower down. Flowers seem to be ignored. By August many leaves are reduced to bare veins. Pupation occurs in an earthen cell in the ground beneath the host plant. Adults emerge from June onwards and by mid July they are usually abundant. They aestivate in July and August (Cox) but this is not consistent as during 2007 adults and larvae were feeding voraciously through the summer in Cassiobury park, it must be mentioned though this followed an unusually cool and wet May and June. Our impression is that large plants host large populations, and smaller plants suffer proportionally much more damage. Despite our many pleasurable hours observing the species we have yet to see them fly. Around Watford they are most easily found on Hogweed (Heracleum sphondylium) but a wide range of plants are eaten; Wild Carrot (Daucus carota), Angelica (Angelica sylvestris), Cow Parsley (Anthriscus sylvestris), Ground Elder (Aegopodium podagraria) and Wild Parsnip (Pastinaca sativa) among others. Formerly a pest of Celery (Linssen).

3-4mm. Black, usually with a strong blue or brassy metallic lustre. Antennal segments 8-11 finely pubescent and dull, contrasting with 1-7, distance between insertion much wider than length of segment 1 (cf Phratora). Head coarsely punctured and with transverse impression between the eyes. Eyes strongly transverse, coarsely faceted. Pronotum microsculptured and with large punctures laterally and basally, disc impunctate at X20 , a feature unique to tumidulus among British Phaedon. Front angles protruding, area behind these raised. Scutellum large and impunctate. Elytra with regular rows of large punctures, microsculptured and very finely punctate between. Tibiae not dilated or toothed on outer side. Segmeny 1 of Tarsi as wide as 3 in Male, narrower in female.

Keyed in Joy). Not dealt with in Bienkowski's excellent aid to British fauna as outside the UK tumidulus is found only in France and Tunisia (Cox).

Description from ten Watford specimens at X20

See ID Aids for a guide to the genus

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