Two hypotheses have been proposed to explain the origin of lifetime monogamy in the Isoptera. The classic explanation is that (1) the male must be present to continually provide sperm for the vast number of eggs produced by the queen (Snyder, 1924: Brian, 1983). Thornhill & Alcock (1983) proposed that (2) synchrony in the availability of receptive females necessitates mate guarding; males subsequently gain if they improve the relative reproductive success of their sole partner.
Our review of the literature on termite flight behaviour, courtship behaviour, and incipient colony development indicates that neither of these two hypotheses satisfactorily explains the evolution of monogamy in termites. Because incipient colonies of lower termites exhibit a very low fecundity, it is doubtful that the continued presence of the male initially was due to the need for a continuous supply of spermatozoa. It is possible, however, that sperm requirements for the fertilization of numerous eggs over an extended period of time may be a factor in the persistence of the termites' monogamous mating system. Female alates are much more dispersed in time than implied by Thornhill & Alcock (1983) and there is no evidence of mate guarding. The importance of mate assistance is, however, supported by the literature. We propose a third hypothesis that incorporates the mate assistance element of the Thornhill & Alcock hypothesis: (3) the monogamous mating system of termites was structured by ecological constraints, namely, the low quality and scattered nature of their food/nesting material and the high costs of searching for a mate.