Morphology and Distribution

When present in the Blattidae, tergal glands almost always occur on the first abdominal tergite. In Blattellidae as many as five segments may be specialized, but most genera in this family have just one tergal gland, usually on segment 1, 2, or 7 (Roth, 1969; Brossut and Roth, 1977). There are many genera where males either have or lack tergal glands. Among species of Parcoblatta, for example, males may have glands on the first tergite only, on the first and second tergites, or they may be absent (Hebard, 1917). In Australian Neotemnopteryx fulva, the tergal gland on the seventh tergite ranges from a pair of dense tufts to a few, nearly invisible, scattered setae; Roth (1990b) illustrates four variations.Uniquely among cockroaches, the gland of Metanocticola christmasensis is on the metanotum (Roth, 1999b). The "best" positions are

Fig. 6.7 Scanning electron micrographs of the tergal gland of male Phyllodromica delospuertos (Blattellidae), in increasing detail. Top, tergite 7, middle, tergal gland, bottom, bristles of the gland. From Bohn (1999), courtesy of Horst Bohn, with permission from the journal Spixiana.

considered to be the more anterior ones, because they draw the female forward, bringing her genitalia into closer alignment with those ofthe male (Roth, 1969).The Anaplectinae and Cryptocercidae have tergal modifications of unknown functional significance because they occur in unusual locations. In the former the tergal gland is on the supra-anal plate (Roth, 1969). In C. punctulatus the gland is located on the anterior part of the eighth tergite, completely concealed beneath the expanded seventh tergite (Farine et al., 1989). Because of its relatively inaccessible position, it is unlikely that it functions to elicit mounting by the female. Nonetheless, females of C. punctulatus have been observed straddling the male prior to assuming the opposed position (Nalepa, 1988a).

Because tergal glands are often markedly different among different genera and species, they can be useful characters in cockroach taxonomy (Brossut and Roth, 1977; Bohn, 1993). Morphologically they range from very elaborate cuticular modifications to the complete absence of visible structures. The glands may take the form of shallow or deep pockets containing knobs, hairs, or bristles (Fig. 6.7), fleshy protuberances, cuticular ridges, groups of agglutinated hairs, tufts or concentrations of setae, or just a few setae scattered on the tergal surface. In species with no externally visible specializations, internal cuticular reservoirs nonetheless may be present (Roth, 1969; Brossut and Roth, 1977). Sometimes secretory cells are merely distributed in the epithelium beneath the cuticle, opening to the exterior via individual pores, and the presence of pheromone-producing cells is inferred from female mounting and feeding behavior (e.g., Blaberus, Archimandrita, Byrsotria—Roth, 1969; Wendelken and

Fig. 6.8 Male tergite 7 of representative species of Phyllo-dromica (Blattellidae: Ectobiinae) showing two sets of tubular pouches underlying the tergal gland. The anterior pair of tubes ("t") are thick and sometimes branched; the posterior pair of tubules ("tl") are very thin and unbranched. The "tl" tubules of Phy. ignabolivari were lost during preparation and are indicated by dotted lines. From Bohn (1993), courtesy of Horst Bohn, and with permission from the Journal of Insect System-atics and Evolution (= Entomologica Scandinavica).

Fig. 6.8 Male tergite 7 of representative species of Phyllo-dromica (Blattellidae: Ectobiinae) showing two sets of tubular pouches underlying the tergal gland. The anterior pair of tubes ("t") are thick and sometimes branched; the posterior pair of tubules ("tl") are very thin and unbranched. The "tl" tubules of Phy. ignabolivari were lost during preparation and are indicated by dotted lines. From Bohn (1993), courtesy of Horst Bohn, and with permission from the Journal of Insect System-atics and Evolution (= Entomologica Scandinavica).

Barth, 1985). In some blattellids the internal glandular apparatus is enormous. Blattella meridionalis has glands that form elongate sacs extending well into the next abdominal segment (Roth, 1985). In the panteli group of Phyllodromica the internal reservoirs consist of two pairs of long tubular pouches (Fig. 6.8). The anterior pair is thick, branched in some species, and open to the exterior via an open bowl or pocket. The posterior pair of tubules is very thin and unbranched, with small openings that lie behind the larger openings of the anterior glands (Bohn, 1993).

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