Pteromorphs
Example of notogasteral ‘pteromorphs’ in Tegoribates latirostris (K.) (Poronoticae, Tegoribatidae, Circumdehiscentiae), in dorsal view. Notogaster separated from the prodorsum and the ventral shield, and seen flat.
– Comments. Pteromorphs (labelled Pt; in yellow) are humeral, laminiform constructions in the form of a cuticular fold (i.e. a border tectum sensu Grandjean, 1934b), the upper and inner walls of which are completely or partially coupled (in this latter case, a ‘limbus’ is well discernible).
The size and outline of pteromorphs vary substantially, from small, triangular shoulders in several genera (e.g. Fig. 1 in Lions, 1978) up to very large, ‘auriculate’ foils in the family Galumnidae and Parakalumnidae (e.g. Fig. 12A in Grandjean, 1936a; Figs 1 and 2 in Travé, 1970). The role of pteromorphs is to protect the legs, their size obviously influencing the efficiency of the protection.
The large-sized pteromorphs may be immovable (e.g. Fig. 2C in Grandjean, 1960b) or movable. In this latter case, the pteromorph-notogaster joint consists of two parts as follows:
(a) a dorsal hinge (line x1-x2) between the notogaster and the upper tectal wall.
(b) a pleat (or ‘pleural subalar pleat’) made by the ventral articular cuticle which connects the border of the inner tectal wall (i.e. the base of the tectum; see Figs 3A, 3B, 3G and 3E in Grandjean, 1966c) with the border of the ventral shield.
The joint may be complete as in this instance or incomplete. Consequently, a forced severance of the notogaster from the prodorsum after heating in lactic acid is often required to confirm the existence of a pteromorph-notogaster joint. It should be noted that the magnitude of the angle made by the articular cuticle allows small pteromorphs without limbus to be distinguished from simple notogasteral overhangs or pads. Indeed, the angle is small in the first ones whereas it is large in the latters (Grandjean, 1956a, p. 205).
The movable pteromorphs rise by elasticity and fall back by the contraction of modified dorsoventral muscles of the humeral region (or ‘alar muscles’) (Grandjean, 1964, pp. 187-194). The alar muscles are remarkable for their insertions. Indeed, the insertions are clearly tendinous on the pleural subalar pleat whereas, on the notogaster, usually the insertions are large and fan-shaped, and may be either non-tendinous or tendinous (but the tendons are short). In this instance, the insertions on the notogaster occupy two areas corresponding to a pair of muscular bundles, namely an anterior area F1 in front of the setae e2 and a posterior area F2 between the seta e2 and the lyrifissure im (strain detector; cf. Barth, 1981).
A third tectum, namely the unpaired border tectum t.lp. (not shown but see diagrammatic Fig. 1B in Grandjean, 1959a), is found posteriorly and laterally in the notogaster. Its role is to protect the connecting band TGS between the notogaster and the ventral shield.
The ‘large suture’ is slightly curved anteriorly between the pteromorphs. It corresponds to a linear, clear-cut, straightforward and unsclerified separation between the prodorsum and the notogaster (see Fig. 1A in Grandjean, 1959c, for an example of a large suture partially sclerified in a member of the Poronoticae where, after heating in lactic acid and severance of the notogaster from the prodorsum, the line of suture seemed clearly damaged). Thus, in contrast with several other Circumdehiscentiae, no residue of the podosoma exists dorsally (i.e. no dorsosejugal zone present). Anteriorly, the notogaster exhibits a wide, trapezoidal clear spot (‘lenticulus’; in green). It is not prominent externally but its internal surface is convex ventrally. Numerous, thin and parallel striae go across it. Clear spots as well as non-cuticular elements associated with them appear to be photosensitive structures (cf. Alberti & Fernández, 1990, and Alberti et al., 1991).
There are four pairs of very thin, short, twisted tubules (labelled Ga, G1, G2 and G3) located where the areae porosae occur in many Poronoticae. Accordingly, it may be thought that the tubules are associated with exocrine glands (see Norton & Alberti, 1997, for a discussion on the secretory function of areae porosae). The minute opening of tubules Ga and G1 are on the wall of the alveole of setae cp and h3, respectively, whereas tubules G2 and G3 open in the vicinity of the alveole of setae h2 and h1, respectively (note: the alveole of these notogasteral setae and of other setae is substantially expanded).
As in several other Poronoticae (data in Grandjean, 1953a, pp. 438-440), the chaetotaxy is of normal, ‘multideficient’ type (i.e. group N5 in Grandjean, 1949a, p. 216; cf. also Grandjean, 1950a, and Lions, 1970). There are ten pairs of setae resulting from the suppression of setae c1, c3, d1, d2, e1 and f1 in the primitive, ‘holotrichous’ chaetotaxy made up of 16 pairs of notogasteral setae (i.e. eight setae on the opisthosomatic segment C, four setae on the segment D, four setae on the segment E, four setae on the segment F, six setae on the segment H, and six setae on the pseudanal segment PS; see e.g. Fig. 30, p. 43, in Travé et al., 1996).
– Abbreviations. h and p, rows of notogasteral setae. c2, cp and f2, notogasteral setae. ia and i, slit-shaped lyrifissures. gla, opening of the exocrine, latero-abdominal glands (or ‘lateral opisthosomal glands’ or ‘opisthonotal glands’ or ‘oil glands’; in red). µ, tendinous insertions. (modified from Grandjean, 1953b).
