Thoracic feet: the jointed legs on the thoracic segments of larvae, as distinguished from abdominal or pro-legs.

Thoracico-abdominal: the first segment of the abdomen when united with the thorax so as to form part of it: =propodeum.

Thoracic pleural bristles: in Diptera, the specialized bristles situated on the pleural region of the thorax.

Thoracotheca: = cytotheca: q.v.

Thorax: the second or intermediate region of the insect body, bearing the true legs and wings: made up of three rings, named in order, pro-, meso-, and meta-thorax: when the pro-thorax is free as in Coleoptera, Orthoptera, and Hemiptera, the term thorax is commonly used in descriptive work for that segment only: in Odonata, where the prothorax is small and not fused with the larger and united meso- and meta-thorax, the term thorax is commonly used for these latter two united, excluding the prothorax.

Thread-plate: an epithelial plate of the embryo from which the terminal threads of the ovarian tubes originate.

Thyridial cell: in Trichoptera: the cell formed by the first fork of median vein; the cell behind Thyridium.

Thyridiate: applied to a wing vein that at one point seems broken so as to permit of a folding or bending; either to pack into a small compa.s.s or to enfold the body.

Thyridium -ii: small, whitish or almost transparent spots near the anastomosis of the disc of the wings in some Neuroptera, or in the recurrent veins in the cubital cellule in some Hymenoptera; also the apical margin of the gastrocoeli, often alone visible: in Trichoptera, specifically, a hyaline spot on second fork of median vein.

Thyrsus: a cl.u.s.ter.

Thysanoptera: fringe-winged: an ordinal term, applied to species with four narrow, similar wings, lengthily fringed; mouth parts fitted for puncturing and sc.r.a.ping; metamorphosis incomplete: the Thripids.

Thysanura: fringe-tails; wingless, mandibulate insects without metamorphosis; with a.n.a.l appendages; body covered with scales; thoracic segments similar.

Tiarate -us: turban or tiara-like.

Tibia -ae: the shank: that part of the leg articulated to the femur basally and which bears the tarsus at the distal end.

Tibial epiphysis: a movable process attached near the base of the inner side of the anterior tibia in many Lepidoptera.

Tibial membrane: in male Cicada, the drum-like vibratory membrane that produces the sound.

Tip: the extremity; the part furthest removed from the base.

t.i.tillator: a small process just below the p.e.n.i.s in some Orthoptera.

Tomentose: covered with fine hair, so matted together that particular hairs cannot be separated.

Tomentum: a form of p.u.b.escence composed of matted, woolly hair: in Diptera applied to a covering of short, flattened, more or less rec.u.mbent, scale-like hair which merges gradually into dust or pollen.

Tongue: an indefinite term, applied usually to the coiled mouth structure of Lepidoptera; the lapping organ of flies; the ligula of bees and wasps and, sometimes also to the hypopharynx of other insects.

Tooth: an acute angulation: a short pointed process from an appendage or margin.

Topomorph -ic: a geographic form, variety or subspecies of a widely distributed species: developed by local environment.

Topotype: is a specimen collected in the exact locality whence the original type was obtained.

Tornal: relating to or concerning the tornus.

Tornus: in Lepidoptera, the junction of the termen and dorsum of wing: = hind or a.n.a.l angle; q.v.

Torose: swelling into knots or protuberances.

Torpid: lying motionless by reason of cold or other natural conditions that unfavorably affect the organism.

Torqueate: with a ring or collar.

Torquillus: = rotula.

Tortilis: twisted.

Tortulose-us: hump-backed; a surface with a few large elevations: beaded; moniliform.

Tortuose -us: irregularly curved and bent; snake-like.

Tortuous: = Tortuose.

Torulus: the basal socket joint of the antenna upon which the organ is articulated for movement in all directions.

Totidem: in all parts; entirely.

T.P. line: transverse posterior line; crossing the primaries of certain Lepidoptera, two-thirds or more from base: = post medial line.

Trabecula: rounded, lobular ma.s.ses of the procerebrum, from which arise the stalks bearing the mushroom bodies: a paired movable appendage in front of the antennae in certain bird-lice.

Trachea -ae: the spirally ringed breathing tube or tubes of insects.

Tracheal gills: the flattened or hair-like processes in aquatic larvae through which oxygen is absorbed from the water.

Tracheary: relating to or composed of tracheae.

Tracheate: supplied with trachea: a general term applied to all articulates that breathe by means of spiracular openings into a system of tubular structures that extend to all parts of the body.

Tracheation: the arrangement or system of distribution of trachea.

Tracheoles: the capillary trachea of the adult as they develop in ma.s.ses in the larva: very small, slender tracheae.

Transection: a cut across, at right angles to the body: transverse section.

Transition zone: is the transcontinental belt in which the austral and boreal elements overlap: it is divided into a humid or Alleghanian area; a western arid area; and a Pacific Coast humid area: all of which see.

Transitory: lasting for a short time only.

Translucent: semi-transparent; admitting the pa.s.sage of light but not of vision.

Translucid: clear: transparent enough to be seen through.

Transparent: so clear as not to obstruct vision.