Retention of Sexually Selected Characters

In several cave-adapted cockroaches, male tergal glands, which serve as close-range enticements to potential mates, do not vary in concert with other morphological features. The glands can be large, or numerous and complex, despite the otherwise troglomorphic features displayed by the male. Trogloblattella nullarborensis is found deep within limestone caves in Australia, and is much larger than other blattellids. It lacks eyes, and has reduced wings and elongated appendages and antennae. Its color, however, has not been modified. Adults are medium to dark brown, and the male has huge tergal glands (Mac-kerras, 1967c; Richards, 1971; Rentz, 1996). Similarly, males in the genus Spelaeoblatta are pale in color and have reduced eyes, brachypterous wings, and long legs and antennae; however, they have large, elaborate tergal glands on two different tergites, and in Sp. myugei, large tubercles of unknown function on tergites 5 through 8 (Fig.

Fig. 1.19 The cave-adapted cockroach species Spelaeoblatta myugei from Thailand. (A) Dorsal view of male. Note large tergal glands on tergites 3 and 4, and paired tubercles on tergites 5-8. (B) Dorsal view of female. (C) Lateral view of male abdomen and its tubercles. From Vidlicka et al. (2003), with permission from Peter Vrsansky and the Taylor & Francis Group.

Fig. 1.19 The cave-adapted cockroach species Spelaeoblatta myugei from Thailand. (A) Dorsal view of male. Note large tergal glands on tergites 3 and 4, and paired tubercles on tergites 5-8. (B) Dorsal view of female. (C) Lateral view of male abdomen and its tubercles. From Vidlicka et al. (2003), with permission from Peter Vrsansky and the Taylor & Francis Group.

1.19) (Roth and McGavin, 1994; Vidlicka et al., 2003). Tergal glands are rare in Nocticola spp., but Noc. uenoi uenoi living in the dark zone of caves on the Ryukyu Islands has a prominent one (Asahina, 1974). The genitalia of male cave cockroaches also can be very complex, despite the regressive evolution evident in other body parts, for example, Nocticola brooksi (Roth, 1995b) as well as other Nocticolidae (Roth, 1988). Mating behavior in cave-adapted cockroaches has not been described.

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