The tergal regions of the mesothorax and of the metathorax are hidden under the pronotum and the elytra when the latter are closed, except that the mesothoracic scutellum is of ten visible - a small triangular or semicircular plate between the bases of the elytra (fig.
The dorsal area of the mesothorax, and also of the metathorax, may be made up of a series of sclerites arranged one behind the other - prescutum, scutum, scutellum and post-scutellum (fig.
3, e, f, g, h), the scutellum of the mesothorax being often especially conspicuous.
R and 2, V.) in Hemiptera is large and free, and the mesothoracic scutellum is usually extensive.
Sc, scutellum; co, cl, m, corium, clavus and membrane of forewing.
The Pentatomidae (shield bugs), some of which are metallic or otherwise brightly coloured, are easily recognized by the great development of the scutellum, which reaches at least half-way back towards the tip of the abdomen, and in some genera covers the whole of the hind body, and also the wings when these are closed.
The Coreidae have a smaller scutellum, and the feelers are inserted high on the head, while in the Lygaeidae they are inserted lower down.
In the curious little Tingidae, whose integuments exhibit a pattern of network-like ridges, the feet are two-segmented and the scutellum is hidden by the pronotum.
The part in contact with the endosperm is plate-like, and is known as the scutellum; the surface in contact with the endosperm forms an absorptive epithelium.
In some grasses there is a small scale-like appendage opposite the scutellum, the epiblast.
Three must be considered: (I) the scutellum, connected by vascular tissue with the vascular cylinder of the main axis of the embryo which it more or less envelops; it never leaves the seed, serving merely to prepare and absorb the food-stuff in the endosperm; (2) the cellular outgrowth of the axis, the epiblast, small and inconspicuous as in wheat, or larger as in Stipa; (3) the pileole or germ-sheath, arising on the same side of the axis and above the scutellum, enveloping the plumule in the seed and appearing above ground as a generally colourless sheath from the apex of which the plumule ultimately breaks (fig.
Especially in relation to the origin of the vascular bundles which supply them, favours the view that the scutellum and pileole are highly differentiated parts of a single cotyledon,and this view is in accord with a comparative study of the seedling of grasses and of other monocotyledons.
The scutellum meanwhile feeds the developing embryo from the endosperm.