Female short winged, sometimes fully winged. Body dark brown, legs yellow, all tibiae yellow at base and apex; antennal segment III yellow with apex brown, IV–VI yellow in basal half or more; major setae and fore wing pale. Head much longer than wide, projecting in front of eyes, cheeks sinuate with pair of prominent setae behind large eyes; ocellar, postocular and mid-vertex setae finely pointed, shorter than eyes; maxillary stylets broad, retracted almost to postocular setae, about one-third of head width apart. Antennae 8-segmented; segment III with 2 long slender sensoria, IV with 4 similar sensoria; segment VIII slender and narrowed to base. Pronotum with 5 pairs of broadly blunt major setae; epimeral sutures usually incomplete; basantra weakly sclerotized, ferna and mesopresternum transverse. Fore tarsi with no tooth. Metanotum reticulate, with one pair of long setae. Fore wing parallel sided, broad, with about 15 duplicated cilia. Pelta broad with prominent lateral wings; short-winged female with anterior pair of sigmoid wing-retaining setae weak on each tergite; tergite IX setae blunt, shorter than tube; tube slightly shorter than head, with several prominent lateral setae.
Male short winged; tergite VI with pair of elongate lateral tubercles bearing a terminal seta, tergites VII and VIII each with smaller lateral tubercles.
The genus Megathrips includes five species from Europe in addition to this one from California. The genus is probably merely an Holarctic subgroup derived from the large genus Bactrothrips that is widespread across the Old World tropics, and M. timidus could equally well be considered a member of Bactrothrips together with the Californian species B. hesperus (see Mound & Tree, 2011). All these species are unusual amongst Phlaeothripidae in having the abdominal tube with prominent lateral setae, and the males commonly have one or more abdominal segments bearing a pair of prominent tubercles laterally (Mound & Palmer, 1983).
Megathrips timidus Cott
Breeding on dead leaves.
Feeding by imbibing fungal spores.