Theca: a case or covering: specifically applied to the fleshy covering of the fly-mouth; to the cases of the Trichopterous larvae; to the lower piece of the male genitalia in Homoptera; and to the outer covering of the pupa.
Thelyotoky: parthenogenetic reproduction when the progeny are all females see Arrhenotoly and Deuterotoky.
Thigh: see femur.
Thigmotactic: contact-loving: applied to species that tend to live close together or in touch, one with the other.
Third longitudinal vein: in Diptera (Will.):= radius 5 (Comst.).
Third posterior cell: in Diptera, = 2d medial 2 (Comst.).
Third submarginal cross-nervure: in Hymenoptera (North.):= radius 4 (Comst.).
Thoracic: belonging or attached to the thorax.
Thoracic dorsal bristles: in Diptera, the specialized bristles on the dorsum of the thorax.
Thoracic feet: the jointed legs on the thoracic segments of larvae, as distinguished from abdominal or pro-legs.