Thrips: Thysanoptera

Thrips are thigmotactic (THIG-mo-TAK-tik), animals that always seek the security of confined and narrow spaces. Both larvae (LAR-vee) and adults live together. The larvae are young of the animal that must change form before becoming adults. Males of fungus-feeding species will defend a single female or groups of females they have mated with as well as the egg masses they produce. These males will compete with one another for females by flicking their abdomens at one another or by attempting to stab each other to death with spines on their legs. In other species, males form groups, or leks (lehks), that attract females that are ready to mate.

Eggs usually hatch in just a few days. In species that reproduce by mating, males develop from unfertilized eggs. Some species reproduce by parthenogenesis (PAR-thuh-no-JEH-nuh-sihs), a process where the larvae also develop from unfertilized eggs. However, these eggs always develop into females.

The development of thrips is unique. Each larval stage ends with the molt, or shedding of the exoskeleton, or hard outer covering. The first two larval stages are active and feed for 2 to 5 days. In winged species, neither of these larvae shows any sign of wing development on the outside of the body. The larval stages are followed by two or three pupal (PYU-pul) stages. The pupa (PYU-pah) is the stage of insect development when the transition between larva and adult becomes obvious. The pupa cannot walk and does not feed. In thrips, the antennae are very small, and the developing wings can clearly be seen on the outside of the pupa. Depending on species, the pupae are sometimes found on leaves, but most species pupate on bark or in leaf litter.

Thrips found on flowers usually produce only one generation per year, but most species reproduce whenever conditions are good. Pest species usually reproduce all the time, with a new generation developing every few weeks.