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JEWEL BEETLE FIELD GUIDE (PDF) ![]() CLICK FOR DOWNLOAD (PDF) ---------------------------------
KINGDOM : Animalia
PHYLUM : Arthropoda
CLASS : Insecta
ORDER : Coleoptera
FAMILY : Chrysomelidae
SUBFAMILY : Sagrinae
GENUS : Sagra
--------------------------------- Beetle identification guide Canada (PDF)CLICK FOR DOWNLOAD (PDF) |
SAGRA LONGICOLLIS FROG-LEGGED BEETLES
Sagra is a genus of beetles belonging to the family Chrysomelidae, commonly referred to as frog-legged beetles or kangaroo beetles.
Found in the jungles of Southeast Asia, this brightly coloured, iridescent species can grow up to 5 cm long. Unlike its namesake,
it doesn't use its hind legs for jumping, instead they're used to cling onto stems and foliage while it eats, its grip aided by scores of tiny
hair follicles that cover the surface of the leg. But there could be more to those legs than just grip, because look at the difference
between the males and females.
If both the males and females move around the trees in much the same way to search for food, there must be a reason why the males
ended up with such monstrous hind legs, which has led researchers to suspect that they could be a sexually selected trait that evolved
as the result of male-on-male contests over females. We’re yet to see a leg battle between two frog-legged leaf beetles, but this
behaviour has been observed in several beetles belonging to a different family - Coreidae - which features similarly oversized hind legs.
The family Chrysomelidae, commonly known as leaf beetles, includes over 35,000 species in more than 2,500 genera, making it one of
the largest and most commonly encountered of all beetle families. Numerous subfamilies are recognized.
Leaf beetles are partially recognizable by their tarsal formula, which appears to be 4-4-4, but is actually 5-5-5. Some lineages are only
distinguished with difficulty from longhorn beetles (family Cerambycidae), namely by the antennae not arising from frontal tubercles.
Adult and larval leaf beetles feed on all sorts of plant tissue. Many are serious pests of cultivated plants, for example the Colorado
potato beetle (Leptinotarsa decemlineata), the asparagus beetle (Crioceris asparagi), the cereal leaf beetle (Oulema melanopus),
and various flea beetles, and a few act as vectors of plant diseases. Others are beneficial due to their use in biocontrol of invasive
weeds. Most Chrysomelidae are conspicuously colored, typically in glossy yellow to red or metallic blue-green hues, and some
(especially Cassidinae) have spectacularly bizarre shapes. Thus, they are highly popular among insect collectors.
The imagoes of leaf beetles are small to medium-sized, i.e. the size of their bodies varies from 1 to 18 millimeters. The bodies of most
of their specimens are arched and egg-shaped, and they often possess a metallic luster or multiple colors. The head's shape (disregarding
antennae and mouthparts) is roundish. In most specimens the antennae are notably shorter than head, thorax and abdomen, i.e. not more
than half their combined length. The second antennae segment is of normal size (which differentiates leaf beatles from the closely
related longhorn beetles). The antennae's segments are of a more or less equal shape, at most they gradually widen towards the tip.
The first segment of the antennae, however, in most cases is larger than the following ones. Like the head, the eyes in most cases are also
of a round shape. The pronotum of leaf beatles is arched in different shapes; only rarely it protrudes in bumpy shapes. The first three
sternites are not fused; there are sutures. All leaf beetles possess wings. Only in some cases they are shortened, and they never leave
more than the last tergum uncovered.
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