Sinus: a curvilinear indentation more or less profound: an excavation as if scooped out: a curved break in an otherwise straight margin. Siphon: a tube-like mouth organ in certain insects: the breathing tube of a Culicid larva: any tubular external process or structure. Siphonaptera: an ordinal name for insects which are wingless: mouth formed for piercing and sucking; saltatorial; transformations complete: the fleas = Aphaniptera; q.v. Siphonata: = Homoptera or, more specifically, plant lice and leaf hoppers. Siphonets: see honey tubes. Siphonophora: = Coccinellidae; the term is preoccupied in the Coelenterates. Siphunculata: the sucking lice. Siphunculus: the suctorial organ of a louse, contained within the tubule: in plant lice =honey tubes; q.v. Situ (in): in its natural place or position. Sixth longitudinal vein: in Diptera; = 1st anal vein (Comst.). Skeleton: the hard chitinous parts which externally (exoskeleton) or internally (endoskeleton) form a protective covering, or serve as points of attachment, to muscles and other soft organs. Skippers: a popular term for Hesperid butterflies: the dipterous larva sometimes found in cheese and other provisions. Slaty: very dark blackish gray with a reddish tinge [neutral with a little Indian red]. Slug: in general, any larva that has a slimy viscid appearance, and the body closely applied to the food plant: more specifically, the larvae of certain saw-flies and of some Coleoptera. S. M. interspace: sub-median interspace in the primaries of Lepidoptera, includes the space between the median and sub-median veins; (cubitus and 1st anal, Comst.). Smaltinus: a dull grayish blue. Smaragdinus: emerald green [pale green]. Smooth: a surface without elevations or indentations. Snout: the prolongation of the head in Rhynchophora at the end of which the mouth parts are situated: see rostrum. Social: living in communities: more especially those species in which undeveloped or worker forms occur and where the colony has a single female head. Soldiers: in termites; forms sexually undeveloped, in which the mandibles are pincer-like and the head is much enlarged: worker majors in certain ants. Solid: applied to an organ usually jointed, when these joints form into one mass; e.g. the capitulum of certain clavate antennae. Solitary-arius: occurring singly or in pairs; not in colonies. Somatic: relating to the body, or abdomen. Somatotheca: that part of pupa covering abdominal rings:= gasterotheca. Somite: = arthromere. Sonifaction: the production of sound: = stridulation; q.v. Sonoran faunal areas: see upper and lower Sonoran. Sonorific: sound producing: applied to stridulating organs. Sordid: dirty; dull. Spadiceous: bay brown [dragon's blood + brown ochre]. Spado: the worker or neuter in bees and ants. Sparse: scattered: single hairs, scales or sculptures set well apart. Spatha: a median piece in male genitalia of aculeate Hymenoptera, covering the bases of the sagitte.