Cardiocondyla is one of the few ant genera in which winged dispersing males coexist with wingless fighter males, which predominantly mate inside their maternal nests. Male polymorphism is not genetically determined but induced by environmental conditions (e.g., a decrease in temperature). The factors leading to the production of winged males were studied in more detail by exposing colonies of C. obscurior to a specific set of rearing conditions. A "stressful" environmental condition (rearing temperature lowered on average by 5°C) experienced for at least two days, the decrease of temperature by a minimum of 3°C, and the addition of protein-rich food triggered the development of winged males. In contrast, a smaller decrease in temperature, starvation, encounters with workers from other species, and encounters with alien, conspecific winged males did not induce the production of winged males. Colonies differed strongly in their reaction to changing environmental conditions, which might indicate a difference in their threshold sensitivity. The results are discussed and compared with data from other dimorphic insect species.
Male dimorphism in insects is often accompanied by alternative mating tactics, which may, together with morphological traits, determine fitness of the different male morphs. Fitness consequences of male head horn size, male-male competition and male nest-staying behaviour were experimentally assessed in Copris acutidens, in which major and minor males can co-occur in nests. Possible differences in their reproductive behaviour and breeding success were assayed in a breeding experiment, in which females were paired with one major male, one minor male, or a pair of major and minor males. The advantage of major males staying in a nest along with a rival male is that major males are reproductively more successful than minor males in this species. The weight of dung transported into nests was significantly less in rearing containers containing two males than in those with a single male of either morph, although it did not differ between major and minor males when kept alone. The results indicate that the presence of a rival male negatively affects male provisioning due to interference from rival males. In contrast, in the present study, an increased incidence of male nest-staying behaviour was recorded in the two- male and one minor male treatment than in the one major male treatment. These results indicate that because of the risk of sperm competition, major males stay longer in nests if a rival male is present. Furthermore, minor males (which are subject to a higher risk of sperm competition) stay longer than major males in nests without a rival male. In other words, the present study revealed an alternative behaviour during the post-copulatory stage associated with horn dimorphism and the presence or absence of a rival male., Mayumi Akamine., and Obsahuje bibliografii