Thrips
Order:
Thysanoptera
Family: Various
Species: Various
Although thrips are very small in size (less than 1/8 in. or 32 mm in length), they usually occur in large numbers and are easily detected. Potted plants with excess water in their drainage pans attract these plant pests flying in from undeveloped lands to neighborhood yards. They can also be brought indoors on cut flowers. Many different accounts, including nursing homes, interiorscapes, greenhouses, grassy areas and pool areas may provide the habitat and food sources to sustain a thrip infestation.
Some members of Thysanoptera, which means "bristle wings," can pierce human skin as they probe for moisture, causing a skin rash. When they swarm in enormous numbers they may annoy people by getting into their eyes, nose, mouth and clothes. In some circumstances, thrips are responsible for reports initially diagnosed as entomophobia or delusionary parasitosis.
Biology and Habits
Adult thrips are very active insects. Species with wings will fly, while others may spring forward when disturbed. After successful mating, eggs are laid on the tissues of plants or inserted into the plants. Thrips may also reproduce by parthenogenesis, that is, reproduction without a male. Generally, there are four or more nymphal instars exhibiting gradual metamorphosis. The latter stages are quiescent (inactive).
Many species have two pairs of wings that are very thin and virtually veinless. The margins of the wing are skirted with close-set long hairs, typical of the order Thysanoptera. The wings are laid back over the abdomen while at rest.
Another identifying characteristic of thrips is that the each tarsus terminates in a cup-like depression surrounding a small bladder structure that can be retracted or protruded by the insect.
The head has compound eyes and less noticeable ocelli. The mouthparts are rasping-sucking. In addition, they are asymmetrical, with two pairs of palps but only one mandible. Magnification is required in order to observe these asymmetric mouthparts.
Control
Careful inspection is needed to identify thrips and to uncover the source of infestation. These insects are phytophagous, so look for host plants, such as potted plants, vegetables or cut flowers. After locating the source of the infestation, collect specimens in vials containing alcohol for accurate species identification.
To reduce and eliminate a thrip infestation, remove excess water around plants and vacuum up the thrips. Discard infested plants, or treat them with insecticides that are not phytotoxic to the host plants. Surface applications may also aid in control efforts.
Always review labeling before selection and application of any pesticide, and document the application.
(Courtesy of the National Pest Control Association.)