Order Hemiptera - True Bugs

• Lists of Homoptera & Heteroptera

Small to large sized insects of widely differing shapes and habits, but all with piercing mouthparts adapted for sucking the juices of plants or animals. The mouthparts form a relatively stout rostrum (often called the 'beak') which is normally held horizontally under the body when not in use. Antennae often quite long, but generally with few segments and nearly always less than ten. Two pairs of wings are normally present, but wingless forms are fairly frequent. The order is split into two distinct suborders - the HOMOPTERA and the HETEROPTERA - based largely on differences in wing structure. Thus, when wings are present, the front pair may be uniformly membranous or stiffened throughout (suborder Homoptera, from the Greek homos = uniform), or the front pair may be clearly divided into two regions - a hardened, leathery basal area and a membranous tip (suborder Heteroptera, from the Greek heteros = different). The hindwings are always membranous.

When at rest, Homoptera fold the wings roof-wise over the body, whereas Heteroptera fold them flat and slightly overlapping. The legs of most bugs are unremarkable, except in a few predatory forms which have raptorial front legs for catching prey, rather like those of Mantids, and in some aquatic forms where the hind legs are somewhat flattened and fringed with hairs for swimming. Cerci are absent, although many Homoptera (e.g. most aphids, family Aphididae) have a pair of tube-like structures at the rear end, called cornicles or siphunculi, from which they can exude a waxy, defensive fluid to repel predators. Also, in some aquatic Heteroptera (e.g. water scorpions and their relatives, family Nepidae) there is a long appendage at the tip of the abdomen, which forms a respiratory siphon or breathing tube. Metamorphosis is simple, with a variable number of nymphal stages depending on species. The true bugs form a large Order with about 70,000 species, of which over 1,500 occur in the British Isles. Many species are of considerable economic importance as pests, not only by causing direct damage or injury to plants and animals, but also by transmitting many viral diseases.

• Agricultural and Horticultural Crop Pests - these include a wide range of homopteran bugs, such as many of the whiteflies (Aleyrodoidea), the aphids and their allies (Aphidoidea), the mealybugs and scale insects (Coccoidea), the jumping plant lice (Psylloidea), and some of the froghoppers or spittlebugs, treehoppers and leafhoppers (Cicadoidea); as well as several heteropteran species, particularly among the squash bugs (Coreidae), the capsid bugs (Miridae), and the shield bugs or stink-bugs (Pentatomidae).

• Biting and Blood-sucking Pests - these include the well known bedbugs (Cimicidae), and a few species of assassin bugs (Reduviidae) and flower bugs (Anthocoridae).

However, the vast majority of Hemiptera are quite harmless insects and some of the predatory forms can be regarded as beneficial when they habitually prey on insect pests. Furthermore, a few species of scale insects (Coccoidea) are of great value in the production of useful commodities, such as shellac, cochineal and various waxes, although nowadays some of these products have been largely replaced by synthetic materials.

• Shellac - a resinous material used in the manufacture of varnishes, polishes and many other products - is prepared from a secretion of the Indian Lac-insect, Laccifer lacca. Similarly, a related insect from Madagascar, Gascardia sp., yields an inferior type of lac containing some waxes, known as 'gum-lac'.

• Cochineal - a red dye used for colouring foodstuffs, medicines and cosmetics - is extracted from the female Mexican Cactus Scale, Dactylopius coccus (= Coccus cacti). The insect lives on one of the prickly-pear cacti of Southern and Central America, but has been cultivated elsewhere in Southern Europe and North Africa.

• Kermes (also known as granum tinctum) - a crimson dye, similar to cochineal - comes from the female scales of Kermes ilicis (= Coccus ilicis), which lives on the twigs and branches of evergreen oaks in Southern Europe and North Africa.

• Waxes - used locally in China, India and elsewhere for making candles and medicinal preparations - are obtained from several Oriental species of homopteran bugs, such as Ericerus pe-la and Ceroplastes ceriferus.

For those with historical interests, the 'manna' of biblical stories is believed, by some, to have been the syrupy honeydew exuded by scale insects and plant lice (in particular the species Trabutina mannipara, which feeds on the tamarix tree of Palestine). In warm, dry climates this exudate quickly solidifies into sugary lumps as the water evaporates, and it is easily collected as it rains down from trees that are heavily infested by these insects - perhaps the origin of the saying, 'manna from heaven'.