Thysanoptera

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Thysanoptera

[‚thī·sə′näp·tə·rə]
(invertebrate zoology)
The thrips, an order of small, slender insects having exopterygote development, sucking mouthparts, and exceptionally narrow wings with few or no veins and bordered by long hairs.

Thysanoptera

 

(thrips), an order of insects having a slender, elongate, and dorsoventrally compressed body. Thrips are usually 0.5–2 mm long (rarely up to 5 mm); tropical species reach a length of 14 mm. The head has asymmetrical mouth-parts that are formed for piercing. The prothorax is free, and the mesothorax and metathorax are fused. The legs have two-jointed, clawless tarsi, which terminate in a bubble-like swelling. The wings either have two or three longitudinal veins or lack venation; there is a fringe of long hairs on the margins. The abdomen consists of 11 segments. The larvae differ from the adults only by the absence of wings. Between the larval stage and the imago there is a motile but nonfeeding stage (two ages) with rudiments of wings; it is analogous to a pupa.

There are about 2,000 species of thrips, 230 of which are encountered in the USSR. The two suborders are Tebrebrantia and Tubulifera. In the former the females are equipped with serrate ovipositors, and they deposit eggs in plant tissues. In the Tubulifera, the females deposit eggs on plant surfaces, in flowers, and in leaf axils.

M. S. GILIAROV

Most thrips are herbivorous. There are some carnivorous species (genera Aelothrips, Scolothrips, and a few others), which feed mainly on the eggs and larvae of herbivorous thrips. Many herbivorous species are serious pests of agricultural crops. Between one and ten generations develop during a vegetative season.

The inflorescences of red clover are damaged by more than 22 species of thrips, including Odonthothrips phaleratus, Odonthothrips confusus, Odonthothrips loti, Odonthothrips intermedius, and Haplothrips niger. Wheat spikes are damaged mainly by Haplothrips tritici. Winter rye and barley are often infested by Limothrips denticornis, Haplothrips aculeatus, Stentothrips graminum, and Anaphothrips obscurus. Industrial crops are invaded by Thrips tabaci, Thrips Unarms, and Thrips flavus. The inflorescences of fruit and berry plants are damaged by Taeniothrips inconsequens, Haplothrips subtilissimus, Haplothrips reuteri, and Zygothrips minutus.

Although thrips are such small insects, they have been found to harbor internal parasites of the order Hymenoptera. The hymenopteron Thripoctenus brui parasitizes Thrips tabaci in Japan. The predators of thrips are trombiculids and small bugs of the genus Triphleps.

Control measures include deep autumn plowing, interrow cultivation, and shallow plowing of stubble. Seeds should be sown at optimal times. Also effective is autumn destruction of fallen foliage in orchards and of various plant remains in fields and gardens. The plants may also be treated with insecticides.

N. P. DIADECHKO