Cassida rubiginosa Muller, 1776
Our most common and widespread tortoise beetle, C.rubiginosa occurs throughout England and Wales, including Anglesea and Man, and southern Scotland to Edinburgh. Further north there are scattered, mostly eastern, records to Elgin. So far absent from the Western and Northern Isles (Cox, 2007). They are common throughout our area in many different habitats, occurence of a foodplant seems to be the only essential factor; open grassland, shrub and wasteland, road verges, parks, gardens and wetland. Cliffs and chalk and gravel pits are quoted in Cox. Adults overwinter in tussocks, among vegetable debris or in moss and appear early in the spring when they may be found by sweeping herbage during the first warm days in March or April depending on season. At this time we have found them several times under dock leaves. A few weeks later they may be swept in numbers from thistles; during April 2007 an area of thistles below Cassiobury park provided dozens of adults by sweeping. This method of sampling will often produce C.rubiginosa and C.vibex together. Adults fly and have been recorded at light, in malaise traps and suction traps (Cox). There is a single generation each year with larvae recorded from June to August and newly emerged adults from late July until September. Larvae have been found on various thistles as well as common Knapweed, feeding on the upper surface of leaves. Adults generally feed on the underside of leaves of a wide variety of plants including thistles, common Knapweed, Greater Burdock, Tansey and Globe Artichoke. They have also been recorded from the flowers of buttercups and Oxeye daisy.

Adults are usually a deep green colour, sometimes with a small dark mark around the scutellum and/or suture, they are thus immediately distinct in the field from C.vibex. These quickly become familiar but lighter specimens occur and these should be examined carefully.

6-7.5mm. Elongate broad oval, pronotum and elytra widely explanate. Head strongly deflexed, black with strong longitudinal furrow between upper level of eyes and fine pale pubescence below antennal insertions, entirely hidden under pronotum. Eyes strongly elongate. Antennae dark with basal segments, usually 1-5, pale, inserted between eyes. Pronotum rounded or very weakly angled anteriorly, hind angles right-angled - look directly down onto the angle ie with the specimen held oblique otherwise they may appear obtuse - hind margin strongly sinuate and excavate around base of scutellum. With large punctures which are wider spaced laterally, punctures are smaller towards disc and may be weakly confluent, surface usually with distinct granulate microsculpture. Cuticle within the punctures varies from opaque and microsculptured to quite transparent so that the head beneath is visible. Scutellum distinct, densely microsculptured, base curved and all margins often abruptly darkened. Elytra green with suture appearing very narrowly darker, often with a dark mark below the scutellum and one or two along basal margin. Preserved specimens gradually lose the green colour and turn yellow. With distinct rows of large punctures although the area around the scutellum and laterally behind middle often confused. Puncturation inside explanate margin consists of a row of transverse impressions, these are variously developed between specimens and may be evanescent or may merge with lateral puncturation towards apex. Humeral area and two interstices raised although to varying degrees and generally weakly so behind middle. Tibiae and tarsi testaceous, femur black basally, testaceous towards apex.

Description taken from three Watford specimens examined at X20.