Odontomachus

A hypothetical biosynthetic sequence has been proposed for the 3-alkyl-2,6-dimethylpyrazines (482) from various species of Odontomachus ants, as shown in Scheme 65. The acyloin (507), prepared by condensation of the pyruvate with active acetate, or the derived dione (508) may condense with the amide (509) of alanine, ultimately giving the 3-alkyl-2,6-dimethylpyrazines (482) (141). A separate biogenesis is envisaged for the 3-alkyl-2,5-dimethylpyrazines (481) such as 3-isopentyl-2,5-dimethyl (20h) and 2,5-dimethyl-3-styrylpyrazines (20j,... 

Citral (123), formic acid (124), and n-undecane (125) are among a host of other compounds identified as formicid alarm pheromones. Recently, Wheeler and Blum (126) reported that alkyl-pyrazines were secreted by Odontomachus spp. in response to foreign stimuli. Some species produced 2,5-dimethyl-3-isopentylpyrazine (XXIX) whereas 2,5-dimethyl-3-pentylpyrazine (XXX) and related compounds were produced by others. Although these compounds are attractants that release attack behavior in Odontomachus workers, ponerine species that form small colonies utilize one of the alkylpyrazines to release escape behavior (127). 

Odontomachus troglodytes demonstrates that of the four compounds produced by workers, three, 2,6-dimethyl-3-butyl pyrazine, and its 3-pentyl and 3-hexyl homologues all release the same behavior pattern in worker ants. These ants are alerted, approach the source with mandibles opened, where some of them attack. The fourth compound, 2,6-dimethyl-3-ethyl pyrazine, has no detectable communicative role between workers, even though it is not the least abundant of the four compounds in the whole secretion. There is no qualitative difference between the behavior patterns released by the three other compounds in the secretion, and the workers response to the whole secretion can be explained in terms of any one of these single components (Longhurst et al., 1978). 

Male ants are often more frail than the workers, and hence ready perception of alarm pheromones should be of advantage to them. The alkyl pyrazines which communicate alarm between workers of Odontomachus troglodytes (see above) release a quite different behavior in males, which retreat and hide imder any suitable object nearby (Longhurst et al., 1978). Alarm pheromones identical to those found in workers are found in males of some species, not in others. In cases where the mandibular glands are used by workers for this purpose, the same or a similar secretion often occurs in males (Crewe, 1973 Brand et al., 1973 Bradshaw et al., 1979b). 

Longhurst, C., Baker, R., Howse, P. E. and Speed, W. S. (1978) Alkyl pyrazines in ponerine ants their presence in three genera, and caste-specific behavioural responses to them in Odontomachus troglodytes. J. Insect Physiol., 24, 833-7. 

African species of Amitermes build hard small mound nests of wood carton and earthen material, often based on a rotting tree stump. The frontal gland secretions of the Amitermes species are, however, totally different from those of Cubitermes. The West African species A. evt/nci/cr contains a sesquiterpene ether, 4,11-epoxy-cis-eudesmane (>90%) (Wadhams et al., 1974) with 10-epi-endesma-3,11-diene, 8-epi-cararrapi oxide, cararrapi oxide, and c/5-/3-ocimene as minor components (Fig. 16.11) (Baker et al., 1978). The secretion is toxic to some ants on topical application, causing motor ataxia, frequently followed by death. Two potential predators, the ants Odontomachus haematodus and Oecophylla longinoda are affected in this way. 

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