Agriculture Reference
In-Depth Information
damage is similar to that caused by flea beetles
(q.v.). Attacks are usually of only minor impor-
tance, but heavily infested plants may become
extensively holed and skeletonized. Noticeable
damage is unusual in the British Isles, and tor-
toise 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.
Fig.
212
Outline of the pronotum of various tortoise
beetles,
Cassida
spp.: (a)
C. nobilis;
(b)
C. nebulosa;
(c)
C. vittata.
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 red-
dish 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
terminat-
ing 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.
as sugar beet. However, eggs are usually de-
posited on weeds such as
Atriplex patula
and
Chenopodium album.
Adults are 5.0-7.5 mm
long, distinctly oval and mainly metallic-green
to brownish above, with irregular black markings
on the elytra and prominent, raised elytral
interstices; the suture between the pronotum
and elytra is distinctly wavy
(Figs 212b and
213).
Both larvae and pupae possess relatively
long, narrow, tail-like processes. The biology
of this species is similar to that of
Cassida nobilis
(above), but there may be two generations
annually.
Cassida vittata
de Villers
Adults or larvae of this often bivoltine species
are associated with various kinds of Cheno-
podiaceae and may, occasionally, cause damage
to sugar beet; infestations in the British Isles,
however, are rare. Adults are 4.5-6.5 mm long
and green with a metallic purplish to golden-
green sutural band along the elytra; they are
readily distinguished from those of
Cassida
Cassida nebulosa
L.
Cloudy tortoise beetle
This widely distributed species, which occurs
throughout Eurasia, is also associated with
Chenopodiaceae, and may occur on crops such
