Pollination

Cockroaches are frequently observed on flowers and many readily feed on offered pollen and nectar (Roth and Willis, 1960). In temperate zones, Blattaria are only occasionally reported from blossoms. Ectobius lapponicus and E. lividus have been observed on flowers of the genera Spirea, Filipendula, and Daucus in Great Britain (Proctor and Yeo, 1972), and Latiblattella lucifrons feeds on pollen of Yucca sp. in southern Arizona (Ball et al., 1942). Nymphs of Miriamrothschildia notulatus and Periplaneta japonica and brachypterous adults of Margattea sat-sumana visit extrafloral nectaries at the base of fleshy, egg-like inflorescences of the low-growing root parasite Balanophora sp. on the floor of evergreen forests in Japan. Visits corresponded with cycles of evening nectar secretion, multiple plants were visited in succession, and pollen grains were observed attached to the tarsi and mouthparts of Mar. satsumana. All observed cockroaches, however, are flightless, suggesting to the authors that cross-pollination is unlikely to be effective (Kawakita and Kato, 2002). An association between cockroaches and flowering plants may be more widespread in the tropics. The strikingly colored Paratropes bilunata visits flowers of the Neotropical (Costa Rica) canopy species Dendro-panax arboreus (Araliaceae). Cockroaches were observed flying during the day to successive inflorescences located 34 m above the ground, ignoring nearby flowers of a different species. The exposed condition of the anthers and stigma of D. arboreus and the observed floral fidelity of the cockroach suggest that Parat. bilunata is a likely pollinator (Perry, 1978; Roth, 1979a). Nagamitsu and Inoue (1997) offer more direct evidence that cockroaches can be the main pollinators of a plant species in the understory of a lowland mixed dipterocarp forest in Borneo. These authors observed blattellid cockroaches feeding on pollen and stigmatic exudate of Uvaria elmeri (Annonaceae) (Fig. 10.3). The visitation time of the cockroaches corresponded with nocturnal dehiscence of anthers, and pollen grains were observed in both the gut and on the undersurface of the head. Because few bees are typically found in canopy collections (Basset, 2001), cockroaches may be among those arthropods filling the pollinator niche in treetops. Of the known cases of cockroach pollination, the degree of floral specificity, distances between visited inflorescences, and consequent effect on gene flow in flowering plants have not been studied.

Fig. 10.3 Blattellid cockroach nymph feeding on pollen of Uvaria elmeri (Annonaceae) in lowland mixed dipterocarp forest in Borneo. From Nagamitsu and Inoue (1997). Photo courtesy of I. Nagamitsu, with permission ofThe American Journal of Botany.

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