Cassida nobilis L Beet tortoise beetle

This beetle is a sporadic and usually minor pest of mangold and sugar beet. Various other members of the Chenopodiaceae are also attacked. Adults and larvae bite holes into the underside of the cotyledons and leaves of host plants, often leaving the upper epidermis intact; initial damage is similar to that caused by flea beetles (q.v.). Attacks are usually of only minor importance, but heavily infested plants may become extensively holed and skeletonized. Noticeable damage is unusual in the British Isles, and tortoise beetles tend to be of greater significance in continental Europe.

BIOLOGY

Adults of this univoltine species overwinter in various sheltered situations and usually emerge in the following April. Eggs are laid singly or in small groups on the underside of the cotyledons or leaves of host plants; they hatch about 2 weeks later. Larvae occur from mid-May onwards. They develop through four instars and are fully grown in about a month. They then pupate, each pupa adhering to the undersurface of a leaf. New adults emerge about 2 weeks later. Larvae of tortoise beetles often cover their bodies with frass and with cast-off skins of earlier instars, presumably for protection.

DESCRIPTION

Adult 3.5-5.5 mm long, elongate-oval and tortoise-like; pronotum and elytra pale brown to greenish-yellow, with deep longitudinal rows of punctures on the latter; there is also often a reddish or purplish metallic band along the elytral suture; pronotum with the hind angles broadly rounded (Fig. 212a) (cf. Cassida vittata, below); underside of body mainly black. Larva up to 6mm long, pale, bluish-green and slug-like, with numerous barbed, lateral spines; body terminating in a simple, forked, tail-like process, which is usually held erect over the abdomen. Pupa 3.5-5.5 mm long, green and flattened; pronotum broad with a spiny border; abdomen with five pairs of fleshy, spinose lateral papillae and four small posterior projections.

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