They
are described as holometabolous (having a complete metamorphosis even though
the nymphs look like small wingless adults) insects with 2 or 3 inactive
pupa-like instars. Thrips are the only members of the 'Exopterygote' (insects
whose wings develop outside there body and thus have externally visible
wing buds in the late nymphal and pupal stages, in comparison with the 'Endopterygote'
insects whose wings develop inside their bodies and are thus not visible
until after metamorphosis) to have developed a true pupal stage. They have
asymetrical mouthparts, having only one (the left) mandible, short 6- to
10-segmented antennae and no cerci. Their wings when present are nearly
equal, very thin with little venation and a lot of hairs making a fringe
around the edge, these hairs greatly increase the effective size of the
wings. Fully winged, brachypterous (with reduced wings) and apterous (wingless)
forms may occurr in the same species, the wingless forms tend to be more
common towards Autumn. They have piercing sucking mouthparts.
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