It has happened more than once, at some point in a presentation or macro class, that my reference to ‘true bugs’ will trigger a response from someone with words to the effect of, “There are false bugs?”.
Outside of entomological circles, the term ‘bug’ broadly covers any small thing that creeps or flies, including insects, spiders and other terrestrial invertebrates. However, to an entomologist, ‘bug’ is specific to the Order Hemiptera. To make the distinction from other creepy-crawlies clear, Hemiptera are referred to as the ‘true bugs’, and includes a large variety of insects commonly known as shield bugs, leafhoppers, froghoppers, bed bugs, pond skaters, cicadas, water bugs, aphids and scale insects.
What are the common characteristics of the Hemiptera?
The most notable common feature is the rostrum or ‘beak’, which are rear-facing (opisthognathous) when at rest. These piercing-sucking mouthparts, actually a modified labium called the sheath, which contain the stylets, which are modifications of the mandibles and/or maxillae. (More on insect mouthparts here) The stylets can penetrate animal or plant tissue by piercing or rasping. Once the tissue is penetrated, digestive enzymes are released through the stylet in saliva and the resulting slurry is imbibed by active sucking. In some bugs such as aphids, the stylets penetrate to reach the plant’s phloem and the turgor pressure actually provides enough flow so that sucking is not required, and the sap throughput is constantly released as honeydew.
Hemipterans also have incomplete metamorphosis (hemimetabolous) where they emerge from the eggs as young nymphs which resemble the adults. Each nymphal stage is called an instar, and typically they will go through several instar stages before becoming an adult. For each stage, the nymph must shed the exoskeleton, and after each moult the wing bud becomes larger. Only the adult will have fully developed wings.
What other shared features to Hemiptera have? Another characterizing feature of Hemiptera can be seen in the name: hemi meaning ‘half’ and ptera meaning ‘wing’. The Hemiptera have two pairs of membranous wings, often with the basal part of the forewing being opaque or leathery and hence called hemelytra.
— Suborder Auchenorrhyncha contains almost all the members of the old suborder Homoptera and includes the cicadas (Family Cicadidae), leafhoppers (Family Cicadellidae), treehoppers (Family Membracidae), planthoppers (Superfamily Fulgoroidea), lantern bugs (Family Fulgoridae) and spittlebugs (Superfamily Cercopoidea). All are plant feeders, and many use sounds to communicate.
— Suborder Coleorrhyncha is an ancient group, commonly known as moss or beetle bugs. Today they are found only in the southern hemisphere in Australia, New Zealand, New Caledonia, and South America. Many have reduced wings and all are flightless and, as the name suggests, they live in moist mossy habitats, often in association with southern beech (Nothofagus) trees.
— Suborder Heteroptera are the true ‘true bugs‘! Once considered an order itself, the Heteroptera are the largest suborder within the Hemiptera (for those who want to severely injure themselves with the taxonomic kerfuffle within Heteroptera–which was formerly Order Heteroptera–read the chapter Classification at Wikipedia) The common feature in many of the Heteroptera can be derived from the Greek name, hetero meaning ‘different’ and ptera meaning ‘wings’. The forewings are fully or partially leathery which, when folded, cover and protect the fully membranous rear wings below.
The Heteroptera contains several infra-orders, but I think the families will be most familiar, and the most recognised of those are the:
Assassin bugs (Family Reduviidae†)
Plant bugs (Miridae)
Bat bugs (Polyctenidae)
— and, some of my favourites, the waterbugs:
Giant water bugs (Belostomatidae†)
Pond skaters (Gerridae†)
Water boatmen (Corixidae†)
Water scorpions (Nepidae†)
Smaller water strider (Veliidae†)
Unlike the other suborders, the Heteroptera are notable because so many of the families are predators (indicated by † above) and some have even taken on parasitic lifestyles. In these instances, the hemipteran rostrum is as efficient at penetrating prey as it is at piercing plants. The parasitic family Cimicidae has about 90 species and all are parasites of warm-blooded birds and mammals, including our bed bugs. The family Polyctenidae are specifically bat parasites.
— Suborder Sternorrhyncha contains a lot of the bugs we love to hate. Aphids (Superfamily Aphidoidea, Family Adelgidae) scale (Superfamily Coccoidea), whitefly (Family Aleyrodidae), mealy bugs (Family Pseudococcidae), and the dreaded grape Phylloxera (Family Phylloxeridae) are all well-known members of this suborder. Sternorrhynchids are all plant feeders and have mouthparts (‘rhynca’) set farther back (‘sternor’) beneath the head.
The Sternorrhynchids often have complex life cycles, including polymorphism (different adult forms within a species), viviparity (live birth), cyclical parthenogenesis (offspring from unfertilized eggs), life cycles with (holocyclic) or without (anholocyclic) sexual stages, as well as heteroecious life cycles that take place on two different hosts.