metasternum


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metasternum

[¦med·ə′stər·nəm]
(invertebrate zoology)
The ventral portion of the metathorax in insects.
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Aplopocranidium however, only differs from Jeremiodes by: the prominently spinose mesonotum, densely granulose to rugulose meso- and metasternum and longitudinally keeled abdominal sternites of both sexes; spinose meso- and metapleurae of females, as well as the simple mesosternum (longitudinally keeled in Jeremiodes) and club-like, gently incurving cerci of males (conspicuously hook-like in Jeremiodes).
Mesonotum with 1 long notopleural, 1 similar postalar and 4 scutellars (lateral pair very short, apical pair somewhat longer than notopleural seta, subparallel); acrostichals lacking; dorsocentrals uniserial, mostly minute, in holotype prescutellar pair obscured by pin (in paratype prescutellars very short, nearly as long as lateral scutellars); mesosternum and metasternum bare between posterior four coxae.
Venter: Prosternum medially elevated, with a conical tubercle directed toward coxae; median part of fused meso- and metasternum and sternites I + II with smooth oval depressions, a conical tubercle on posterolateral margin of meso- and metasternum reaching meso- and metacoxae; sternites III-VII separated by deep transversal grooves; abdominal spiracles II-IV ventral, V-VII placed on laterally projecting tubercles and visible from above, spiracle VII terminal on paratergites VIII.
This is the first known flightless Trichiorhyssemus species in the world, thus readily recognized by characters related to microptery, like the indistinct humeral callus and the shortened metasternum.
Metasternum concave, with a deep vertical sulcus from the middle of the anterior portion to that of the posterior portion, and longerthan ventrite 3; metepisternite distinct, not concealed by elytra; mesepisternum complete, reaching the marginal line of the metasternum.
The species of the genus Scybalophagus can be recognized from other New World canthonines by the following combination of characters: Medium to small size, color black, with or without copper reflections; clypeus bidentate (with two small medial teeth), teeth separated by U-shaped emargination, or cuadridentate (with two small medial teeth and smaller, lateral teeth); head lacking horns or tubercles; pronotum strongly transverse; elytra convex, lateral and apical margins rounded, lacking carinae; pygidium longer than wide, basal margin angulose; metasternum gibbose in middle; protibiae tridentate, with denticles on basal half; meso- and metatibiae with well developed transversal carinae on apical third (Figs.
Pro, meso y metasternum con vestidura setifera intensa y combinada (mediana y larga).
Metasternum anteriorly tumid, with small, shallow punctures denser at apex and sides.
Mesosternum and metasternum with sparse and inconspicuous small granules.
Integument: Body surface rather dull, almost glabrous; head, pronotum, scutellum, clavus, corium, connexivum, pro-, meso-, and metapleura, metasternum, abdominal sterna, male genital capsule and female genital plates densely punctate.
5 (but less than 4) times that of the second segment; the mesosternum less than twice length of metasternum, and the short, conate parameres, whereas the sister group relationship between Gerris and Aquarius is diagnosed by the basis of the first antennal segment being shorter than half the body length; the absence of a pale median stripe on the pronotal lobe, the thickened fore femora of the female, and the incrassate fore femora of the male (Damgaard and Cognato, 2005).