In Existing Burrows and Nests

Some cockroaches specialize in using the niche construction, food stores, and debris of other species. Whether these cockroaches elude their hosts or are tolerated by them is unknown. Of particular interest are the cockroaches that live with insectivorous vertebrates such as rodents and some birds. How do the cockroaches avoid becoming prey?

Insect Nests

A number of cockroaches live in the nests of social insects, although these relationships are rather obscure. Some cockroach species collected in ant and termite colonies have been taken only in this habitat (Roth and Willis, 1960), and are presumably dependent on their hosts. In others, the relationship is more casual, with the cockroaches opportunistically capitalizing on the equable nest climate and kitchen middens of their benefactors. Several species of the genus Alloblatta, for example, scavenge the refuse piles of ants (Grandcolas, 1995b). Similar garbage-picking associations are found in Pyc. surinam-ensis with the ant Campanotus brutus (Deleporte et al., 2002), and in nymphs of Gyna with Dorylus driver ants (Grandcolas, 1997a). Occasional collections from insect nests include the Australian polyphagid Tivia australica, recorded from both litter and ant nests, and the blattellid Paratemnopteryx australis, collected from under bark, in litter, and from termite (Nasutitermes triodiae) nests (Roach and Rentz, 1998). In the United States, Arenivaga bolliana and A. tonkawa have been taken from both nests of Atta texana and burrows of small vertebrates (Roth and Willis, 1960; Waller and Moser, 1990). In Africa, Er. capensis has been collected in open bush, in human habitations, and in termite mounds, and is just one of several taxa, including Periplaneta, that exploit both human and insect societies (Roth and Willis, 1960).

The records we have of more integrated myrme-cophiles include the New World genera Myrmecoblatta and Attaphila. The polyphagid Myrmecoblatta wheeleri is associated with nests of Solenopsis geminata in Guatemala (Hebard, 1917), and with the carpenter ants Camponotus abdominalis in Costa Rica and C. abdominalis floridanus in Florida. Deyrup and Fisk (1984) observed at least 20 Myr. wheeleri of all sizes when a dead slash pine log was turned over in scrubby flatwoods habitat in Florida. All Attaphila spp. (Blattellidae) are associated with leaf-cutting ants in the genera Atta and Acromyrmex (Kistner, 1982). The best known is Attaphila fungicola (Fig. 1.16B), a species that lives in cavities and tunnels within the fun gus gardens of Atta texana. Both male and female cockroaches have been collected from A. texana nests in Texas (Wheeler, 1900), but only females have been collected in Louisiana (Moser, 1964). Within the nest, Att. fungicola ride on the backs or the enormous heads of soldiers, which "do not appear to be the least annoyed" (Wheeler, 1900). The cockroach mounts a passing host by grabbing the venter or gaster, then climbing onto the mesonotum; they ride facing perpendicular to the long axis of the ant's body. The weight of the cockroach may cause the ant to topple over (J.A. Danoff-Burg, pers. comm. to WJB). Perhaps for this reason, Attaphila chooses for steeds the soldiers, the largest ants in the colony. The cockroaches run along with ants as well as riding on them, and can detect and orient to ant trail pheromone (Moser, 1964), presumably via a unique structure on the maxillary palps (Brossut, 1976). Wheeler (1900) originally thought that the cockroaches fed on the ant-cultivated fungus within the nest, but later (1910) decided that they obtain nourishment by mounting and licking the backs of soldiers. It is, of course, possible that they do both.

Recently, another myrmecophile has been described from jungle canopy in Malaysia, leading us to believe that there are many more such associations to be discovered in tropical forests. The ovoviviparous blattellid Pseudo-anaplectinia yumotoi was found with Crematogaster de-formis in epiphytes (Platycerium coronarium) exposed to full sunlight 53 m above the ground. The leaves of these stag's horn ferns form a bowl that encloses the rhizome, roots, and layers of old leaves within which the ants and cockroaches live. More than 2800 Ps. yumotoi were collected from one nest of about 13,000 ants. The ants protect the cockroaches from the attacks of other ant species. Living cockroaches are not attacked by their hosts, but ants do eat the dead ones (Roth, 1995c; T. Yumoto, pers. comm. to LMR). At least two cockroach species exploit the mutualism between ants and acacias. Blattella lo-biventris has been found in swollen acacia thorns together with Crematogaster mimosae (Hocking, 1970). Female Nyctibora acaciana glue their oothecae near Pseudo-myrmex ant nests on acacias, apparently for the protection provided by the ants against parasitic wasps (Deans and Roth, 2003).

Several species of cockroaches in the genus Nocticola have been found within the nests of termites but nothing is known about their biology or their relationship with their hosts (Roth and Willis, 1960; Roth, 2003b). The majority of these are associated with fungus-growing termites (Macrotermes and Odontotermes), which in the Old World are the ecological equivalents of Atta. This strengthens the suggestion that fungus cultivated by social insects may be an important dietary component of cockroach inquilines. Many cockroach species can be found in deserted termite mounds (Roth and Willis, 1960).

Few cockroaches have been found in nests of Hy-menoptera other than ants. The minute (3 mm) species Sphecophila polybiarum inhabits the nests of the vespid wasp Polybia pygmaea in French Guiana (Shelford, 1906b). Apparently the cockroaches feed on small fragments of prey that drop to the bottom of the nest when wasps feed larvae. Parcoblatta sp. (probably Parc. vir-ginica) are commonly found (68% of nests) scavenging bits of dropped prey and other colony debris in subterranean yellowjacket (Vespula squamosa) nests at the end of the colony cycle (MacDonald and Matthews, 1983). Similarly, Oulopteryx meliponarum presumably ingest excreta and other debris scattered by the small stingless bee Melipona. Additional associations are discussed in Roth and Willis (1960).

Cockroaches living in the nests of social insects profit from protective services, a favorable microclimate, and a stable food supply in the form of host-stored reserves and waste material. The only benefit to the hosts suggested in the literature is the opportunity to scavenge the corpses of their guests. Ants generally ignore live Attaphila in the nest (Wheeler, 1900), but the mechanism by which the cockroaches are integrated into colony life has not been studied. Like other inquilines, however, the cuticular hydrocarbons of these cockroaches may mimic those of their hosts. Gas chromatography indicates that the surface wax of Ps. yumotoi is similar to that of their ant hosts (T. Yumoto, pers. comm. to LMR), but it is yet to be determined whether these are acquired from the ants by contact or ingestion, or if they are synthesized de novo. Cuticular hydrocarbons are easily transferred by contact between two different species of cockroaches. After 14 days in the same container N. cinerea and R. maderae merge into one heterospecific group with cuticular profiles that show characteristics of both species (Ever-aerts et al., 1997). Ants can acquire the hydrocarbons of a non-myrmecophile cockroach (Supella longipalpa) via physical contact; these ants are subsequently recognized as foreign by their nestmates and attacked (Liang et al., 2001). Individuals of Attaphila fungicola spend so much time licking soldiers (Wheeler, 1910) that these myrme-cophiles may be internally acquiring and then reusing epicuticular components of their host.

Vertebrate Burrows

Most records of Blattaria in vertebrate burrows come from deserts (discussed below), as the high moisture content of these habitats is advantageous in arid environments. Cockroach food sources in these subterranean spaces include organic debris, and the feces, cached food, and dead bodies of inhabitants (Hubbell and Goff, 1939).

Roth and Willis (1960) indicate that cockroach species found in animal burrows are usually different than those that inhabit caves. Richards (1971), however, suggests that burrows may be important as intermediate stops when cockroaches move between caves, and gives as example the often cavernicolous species Paratemnopteryx rufa found in wombat burrows.

Bird Nests

Cockroaches are only rarely associated with the shallow cup-type nest typical of many birds. The one exception known to us is Euthlastoblatta facies, which lives in large numbers among twigs in the nests of the gray kingbird in Puerto Rico (Wolcott, 1950). Most records are from the nests of birds that breed gregariously and construct pendulous, teardrop-shaped nests up to 1 m long (Icteridae) or large, hanging apartment houses of dry grass (Plo-ceinae). Roth (1973a) collected about 10 species of cockroaches in the pendulous nests of an icterid (probably the oriole, Cassicus persicus) in Brazil. Schultesia lampyridi-formis was found in 2 of 7 nests of Cassicus about 18 m above ground in the Amazon. Van Baaren et al. (2002) found 5 species in icterid bird nests in French Guiana: Schultesia nitor, Phoetalia pallida, Pelmatosilpha guianae, Chorisoneura sp., and Epilampra grisea. Immature cockroaches were common in the nests of Ploceinae in Madagascar and the Ivory Coast; all nests of Foundia spp. examined in Madagascar harbored cockroaches restricted to this habitat (Paulian, 1948). Griffiniella heterogamia lives in nests of a social weaver bird in southwest Africa (Rehn, 1965). Most icterid nests inhabited by the cockroaches were abandoned, and a few carried the remains of dead young birds. The cockroaches are probably scavengers and may also occupy the nests while birds are present (Roth, 1973a).

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