Cockroaches Specific species

Fig. 6.1b). Although they are probably present in most cockroach species, sex-specific contact pheromones have been identified in only a few species. They are thought to be distributed throughout the epicuticular surface and are perceived by means of antennal contact and with the mouthparts. Female-produced contact pheromones elicit courtship responses in males however, in some cockroaches, stridulation and hissing may combine with, or operate in place of, contact chemore-ception. In addition, male contact pheromones may function to inhibit courtship in other males. 

P americana is one of just a few species of insects in which both peripheral and central olfactory processing have been studied. In contrast to many short-lived lepidopterans, in which the male antenna is highly specialized for sex pheromone reception, the antennae of male cockroaches contain numerous food-responsive sensilla. In addition to olfactory sensilla, the antennae also house mechano-, hygro-and thermoreceptors, as well as contact chemoreceptors (Schaller, 1978 review Boeckh et al., 1984). Extensive ultrastructural and electrophysiological evidence has demonstrated that morphologically defined sensillum types house receptor cells of specific functional types (Sass, 1976, 1978, 1983 Schaller, 1978 Selzer, 1981, 1984 review Boeckh and Ernst, 1987). Boeckh and Ernst (1987) defined 25 types of cell according to their odor spectra, but of the 65 500 chemo- and mechanosensory sensilla on the antenna of adult male P. americana, an estimated 37 000 house cells that respond to periplanone-A and periplanone-B. 

Everaerts et al. (1997) reported species-specific profiles based on comparison of CHCs from L. maderae with those from Nauphoeta cinerea, not an urban pest but widely used by herpetologists. In the same paper the authors mentioned unpublished results on a good species-specific correlation of CHCs in 30 cockroach species. 

Specific cuticular mixtures have also been used in robot cockroach tests (Halloy et al., 2007), and this application could be extended to various species for a futuristic approach to pest control. 

Everaerts, C., Farine, J.-P. and Brossut, R. (1997). Changes of species specific cuticular hydrocarbon profiles in the cockroaches Nauphoeta cinerea and Leucophaea maderae reared in heterospecific groups. Entomol. Exp. Appl., 85, 145-150. 

There are two main ways of gaining specificity in pheromone signals. One is by the evolution of a large unique molecule. Peptide pheromones, using the 20 coded amino acids available in eukaryotic systems, offer an extraordinary variety of unique sequences with a five amino-acid polypeptide there are 20 ( 3.2 million) (Browne et al., 1998). For example, two related species of the newt Cynops have species-specific decapeptide pheromones which differ by just two amino acids (Yamamoto et al., 2000). Among insects, a very few species use a unique complex molecule as a single component pheromone for example, periplanone-B is the sex pheromone of the American cockroach (Periplaneta americana) (Roelofe, 1995). 

Once consumed, allelochemics have assorted deleterious effects. Otherwise, they can pass through the insect with no effect, be sequestered, or detoxified. Many enzyme systems are involved in biochemical defense against plant allelochemics, but the most familiar and perhaps most important are the mixed function oxidases. Brattsten (1979) describes the three major characteristics that contribute to their importance in biochemical waste disposal (i) they catalyze numerous oxidative reactions that produce more polar and hence more excretable compounds, (ii) they are non-specific in that a wide range of chemicals are acceptable substrates, (iii) they can adjust rapidly (within minutes) to the presence of allelochemics or synthetic insecticides via induction. The MFO detoxification system is not confined to insects MFO activity has been identified in a wide range of vertebrates and invertebrates. A variety of flies, mosquitoes, cockroaches, crickets and a minimum of 40 species of Lepidoptera (as well as representatives from other insect orders) possess MFO activity (review Brattsten, 1979). 

The African locust converted the same substrate (509) into a 7-hydroxy product (511) and a 13-hydroxylated product (512). It is noteworthy that the Afriean locust and cockroach showed clear species specificity for introduction of oxygen function (Darrouzet et al., 1997). 

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