Wheeler The Social Insects

There are distinct advantages to living within your food source. Logs offer mechanical protection and refuge from a number of predators and parasites, with an interior temperature and humidity generally more moderate than that of the external environment. Abundant if low-quality food is always close at hand. One disadvantage is that when on this fixed diet, a wood-feeding dictyopteran would forfeit the opportunity to move within the habitat seeking specific nutrients and nitrogenous bonanzas

(e.g., bird droppings) as its developmental and reproductive needs change. Reliance on slowly accumulated reserves and the use of food originating from conspecific sources, then, would become considerably more important, particularly in those stages with a high nitrogen demand—reproducing females and young nymphs (Nalepa, 1994).

Termites inherited from cockroaches a suite of interindividual behaviors that allow for nitrogen conservation at the colony level and provide a means of circulating it among individuals within the social group (Table 4.6). These include cannibalism, necrophagy, feeding on exuviae, and coprophagy. Two behaviors of particular note are allogrooming and trophallaxis, first, because they supply the organizational glue that keeps termite colonies cohesive and functional, and second, because among cockroaches these behaviors are only known from wood-feeding species. Allogrooming has been noted in Panesthia (M. Slaytor, pers. comm. to CAN) and Crypto-cercus, and in the latter it occurs exactly as described in termites by Howse (1968). The groomer grazes on the body of a conspecific, and the insect being groomed responds by rotating its body or appendages into more accessible positions (Fig. 5.5B).As with termites, the nymph being tended may enter a trance-like state and afterward remain immobile for a short period of time before resuming activity (Nalepa and Bandi, 2000).

Trophallaxis is the circulatory system of a termite colony. It is the chief mechanism of disseminating water, nutrients, hormones, dead and live symbionts, and the metabolic products and by-products of the host and all its gut symbionts. Stomodeal trophallaxis (by mouth) occurs in all termite families, and proctodeal trophallaxis (by anus) occurs in all but the derived family Termitidae (McMahan, 1969; Breznak, 1975, 1982). Both types of trophallaxis occur in wood-feeding cockroaches, and in these taxa the behaviors occur in the context of parental care. Salganea taiwanensis feeds its young on oral secretions (T. Matsumoto, pers. comm. to CAN; Fig. 8.3B), and Cryptocercus adults feed young nymphs on hindgut fluids (Seelinger and Seelinger, 1983; Nalepa, 1984; Park et al., 2002).

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