Thysanoptera Thysanura Trichoptera

THYSANOPTERA Introduction

Thrips are 0.75-2.0 mm long and have a slightly compressed or flattened body. They are usually pale yellow to darkbrown, to black. Wings are long and narrow with few or no veins; there is an outer marginal row of long, delicate setae. Mouthparts are piercing-sucking. Mostthrips feed onplantjuices, and they are commonly found in flowers and leaves. Some feed on fungi, and a few species are predaceous on mites and other insects. Many of the species that feed on grasses and grains migrate in large numbers when the grain moisture content decreases, which is usually in the fall. Eggs are laid in the spring by females that overwintered in protected locations. Eggs are deposited on the surface of leaves or bark, or inserted into plant tissue; hatching occurs in 2-20 days, depending on temperature. Development from egg to adult is usually through four or five instars. The first two feeding instars are called larvae; the third instar does not feed and is called a prepupa; and the fourth instar is called a pupa. The pupa is sometimes enclosed in a cocoon. There are several generations per year.

Pest status is based on their biting people and being a nuisance during some seasons. Occasionally large numbers of thrips will gather around the outside of buildings, and move inside through doors and windows. Bites on the skin may be painful and result in a skin rash and an itching reaction. The itching produced by thrips bites is probably a result of their attempts to obtain water from the skin surface. Volatile components of sweat, including carponic and lactic acid, are attractive to some thrips, such as Limothrips cerealium, and Haplothrips aculeatus. Thrips that bite and provoke skin rashes include species that typically feed on cereals and grasses, such as Chirothrips aculeatus, and L. cerealium, the pear thrips, Taenio-thrips inconsequens, and the onion thrips, Thrips tabaci. Species reported to cause skin rashes include Gynaikothrips ficorum in Algeria, Caliothrips indicus in Sudan, T. maginis in Australia, and

L. denticornis in Germany. A few are known to pierce the skin and suck blood. This habit has been reported for adults of Karnyothripsflavipes, a predator of scale insects in the Mediterranean region. Second instars ofthe plant-feeding thrips, Thrips tabaci and Frankliniella moultoni, have been reported to bite. The predatory species Scolothrips sexmaculatus, Leptothrips mali, Aeolothripsfasciatus, and A. kuwanaii also bite people.

Thripidae

This is a large family and it contains many economically important species. The wings are pointed at the tips and the antennae are 6-9-segmented. Most species are plant feeders, and some are pests ofagricultural crops.

Greenhouse thrips, Heliothrips haemorrhoidalis Adult females are about 1.2 mm long and dark brown to nearly black. The body is reticulated and the antennae are eight-segmented. Males are relatively unknown. Eggs are laid in plant tissue. The nymphs are pale brown. There are several generations per year. This species is nearly cosmopolitan and attacks a variety of ornamental plants indoors and outdoors. It is common in greenhouses, and brought into buildings on plants.

Cereal thrips, thunder fly, Limothrips cerealium Adults are about 1.5 mm long, and the body is black. They are common in cereal-growing areas, and often occur in large numbers in fall, prior to grain harvest. During periods when this species migrates, aerial densities ofadults flying above wheat can exceed two thrips per cubic meter. Gravid females emerge from hibernation in early spring and fly to grasses and cereals to lay eggs. The next generation of adults emerge in summer, and continue to feed until the cereal begins to senesce. When the moisture content of the grain declines to about 45%, the adults no longer feed and begin to disperse. Females fly to hibernation sites in numbers comparable to migrating locusts and aphids. Migrating thrips can be carried by wind to buildings about i km from the host cereal. Large numbers can enter buildings and cause irritation to skin and eyes. Adults will move into small cracks and crevices thatare about 0.3 mm wide, and sometimes this behavior activates electronic fire-detection systems. They often find suitable harborage in several types of fire detectors, including those based on ionization or optical scatter. In two-story buildings, they are usually found on the upper floors.

Flower thrips, Frankliniella tritici Adults are 1.2-1.3 mm long, slender, and yellow to yellowish orange. This species is common on ornamental flowers and broughtindoors on cut flowers. It is known to bite people indoors.

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