Longhorn Beetles

Jan 29, 2012 News

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Longhorn beetles (Cerambycidae; also known as long-horned beetles or longicorns) are a cosmopolitan family of beetles, typically characterized by extremely long antennae, which are often as long as or longer than the beetle’s body. In various members of the family, however, the antennae are quite short and such species can be difficult to distinguish from related beetle families such as Chrysomelidae. The family is large, with over 20,000 species described, slightly more than half from the Eastern Hemisphere. Several are serious pests, with the larvae boring into wood, where they can cause extensive damage to either living trees or untreated lumber or, occasionally, to wood in buildings; the old-house borer, Hylotrupes bajulus, being a particular problem indoors.
A number of species mimicants, bees, and wasps, though a majority of species, are cryptically coloured. The rare titan beetle (Titanus giganteus) from northeastern South America is often considered the largest, though not the heaviest, and not the longest including legs, insect, with a maximum known body length of just over 16.7 centimetres (6.6 in).
As with many large families, different authorities have tended to recognize many different subfamilies, or sometimes split subfamilies off as separate families entirely (e.g.,Disteniidae, Oxypeltidae, and Vesperidae); there is thus some instability and controversy regarding the constituency of the Cerambycidae.
There are few truly defining features for the group as a whole, at least as adults, as there are occasional species or species groups which may lack any given feature; the family and its closest relatives, therefore, constitute a taxonomically difficult group, and relationships of the various lineages are still poorly understood.
Generally beetles are the group of insects with the largest number of known species. They are placed in the order Coleoptera which contains more described species than in any other order in the animal kingdom, constituting about 25 per cent of all known life-forms.
In fact, 40 per cent of all described insect species are beetles which amounts to about 350,000 species, and new species are frequently discovered. Estimates put the total number of species, described and un-described, at between five and eight million.
Reports are that beetles can be found in almost all habitats, but are not known to occur in the sea or in the Polar Regions.
They interact with their ecosystems in several ways and often feed on plants and fungi, break down animal and plant debris, and are known to consume other invertebrates as well. Some species are prey of various animals including birds and mammals.
Certain species are however considered agricultural pests, while other species are regarded as important controls of agricultural pests. For example, beetles in the family Coccinellidae (ladybirds or ladybugs) consume aphids, scale insects, thrips, and other plant-sucking insects that damage crops.
The general anatomy of beetles is quite uniform, although specific organs and appendages may vary greatly in appearance and function between the many families in the order.
Like all insects, beetles’ bodies are divided into three sections: the head, the thorax, and the abdomen. When viewed from below, the thorax is that part from which all three pairs of legs and both pairs of wings arise. The abdomen is everything posterior to the thorax. When viewed from above, most beetles appear to have three clear sections, but this is deceptive: on the beetle’s upper surface, the middle ‘section’ is a hard plate called the pronotum, which is only the front part of the thorax; the back part of the thorax is concealed by the beetle’s wings.
Like all arthropods, beetles are segmented organisms, and all three of the major sections of the body are themselves composed of several further segments, although these are not always readily discernible. This further segmentation is usually best seen on the abdomen.
Beetles are generally characterised by a particularly hard exoskeleton and hard forewings (elytra).
The beetle’s exoskeleton is made up of numerous plates called sclerites, separated by thin sutures. This design creates the armoured defences of the beetle while maintaining flexibility. The elytra are not used for flight, but tend to cover the hind part of the body and protect the second pair of wings (alae). The elytra must be raised in order to move the hind flight wings. A beetle’s flight wings are crossed with veins and are folded after landing, often along these veins, and are stored below the elytra.
In some beetles, the ability to fly has been lost. These include the ground beetles (family Carabidae) and some ‘true weevils’ (family Curculionidae), but also some desert and cave-dwelling species of other families.
Many of these species have the two elytra fused together, forming a solid shield over the abdomen. In a few families, both the ability to fly and the elytra have been lost, with the best known example being the glow-worms of the family Phengodidae, in which the females are larviform throughout their lives.
Beetles have mouthparts similar to those of grasshoppers. Of these parts, the most commonly known are probably the mandibles, which appear as large pincers on the front of some beetles. The mandibles are a pair of hard, often tooth-like structures that move horizontally to grasp, crush, or cut food or enemies. Two pairs of finger-like appendages are found around the mouth in most beetles, serving to move food into the mouth. These are the maxillary and labial palpi.
The eyes are compound and may display remarkable adaptability, as in the case of whirligig beetles (family Gyrinidae), in which the eyes are split to allow a view both above and below the waterline. Beetles’ antennae are primarily organs of smell, but may also be used to feel out a beetle’s environment physically. They may also be used in some families during mating, or among a few beetles for defence.
Beetles and their larvae have a variety of strategies to avoid being attacked by predators or parasitoids. These include camouflage, mimicry, toxicity, and active defence.
Camouflage involves the use of colouration or shape to blend into the surrounding environment. This sort of protective coloration is common and widespread among beetle families, especially those that feed on wood or vegetation, such as many of the leaf beetles (family Chrysomelidae) or weevils. In some of these species, sculpturing or various coloured scales or hairs cause the beetle to resemble bird dung or other inedible objects. Many of those that live in sandy environments blend in with the coloration of the substrate.
(Source: Wikipedia – The Free Online Encyclopedia)

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