Hemiptera

“In a season the potential descendants of one female aphid contain more substance than 500 million stout men” – Thomas Henry Huxley (1858)

The Hemiptera, also called “true bugs” or simply “bugs”, are the 5th largest order of insect (50,000-80,000 species) and include the cicadas, aphids, planthoppers, leafhoppers, froghoppers and shield bugs. Hemiptera are characterised by possessing piercing and sucking mouthparts and having one pair of wings half the size of the other (hence ‘Hemiptera’).

IMPORTANCE. True bugs are commonly pests and use their stylets (modified tubular mouthparts) to pierce plant tissue and suck fluids (usually phloem or xylem) which can slow down plant growth and even transmit plant pathogens. Aphids for example are abundant and generalist pests of forestry and agricultural, which reproduce rapidly and become quickly resistant to pesticides. Several beneficial predatory hemipterans, such as assassin bugs, pirate bugs and ambush bugs, can be used for the biological control of such things as aphids, thrips and cottony cushion scale.

CLASSIFICATION. Hemiptera classification has changed significantly in recent years, with the group being classically split into the ‘old orders’ of Heteroptera (different wings) and Homoptera (similar wings). In modern taxonomy, heteroptera is a sub-order and homoptera is split into sub-orders Auchenorrhyncha and Sternorrhyncha. The heteropterans include the seed bugs, shield bugs, capsids, bed bugs and water bugs and are characterised by having membranous hindwings behind leathery forewings. The Sternorrhynchans include the inactive aphids, psyllids, whitefly and coccids whereas the Auchenorrhynchans include the jumping leafhoppers, planthoppers, froghoppers (aka spittle bugs) and cicadas. Auchenorrhyncha is further divided into Cicadamorpha and Fulgoromorpha.

IDENTIFICATION. To distinguish between the sub-orders of hemiptera, one must look at the position of the rostrum. In heteroptera the rostrum arises from the front of the head, whereas the beak arises from the rear of the head in auchenorrhyncha and from nearly between the front legs in sternorrhyncha (see pictures). Heteroptera can be easily distinguished by spotting the flat leathery forewings and the prominent triangular scutellum between the wings. In comparison the auchenorrhyncha lack the scutellum and leathery wings, and the wings are held arched (tent-like) over the abdomen at rest. Cicadamorpha and Fulgoromorpha can be identified using form of the head and placement of coxae.

rostrums

LOCOMOTION. Hemipterans are notable for their variety of methods of transport. Several families of heteroptera, such as the water boatmen, water scorpians and backswimmers have adapted to an aquatic lifestyle. They have adapted paddles from legs to help them move through the water. Pondskaters use the surface tension of the water to effectively walk on water, and are the only truly marine group of insects. Some hemipterans even exploit the Marangoni effect propulsion gained from releasing a soap-like substance into the water to break the surface tension. Other true bugs employ a sedentary lifestyle (like apterous aphids) or fly with help of wind (alate aphids) but the most notable form of transport is the jumping (saltation) which the hoppers elicit by releasing energy (sometime elastic) and using hind legs to propel them at speeds of 2.7 metres per second. One well known lifestyle of an auchenorrhynchan is that of the cicada (see video)

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