A summary of literature, documented observations and field studies finds evidence that mothers actively defend offspring in at least eight species and three gen

Many organisms exhibit phenotypic plasticity; producing alternate phenotypes depending on the environment. Individuals can be plastic (intragenerational or direct plasticity), wherein individuals of the same genotype produce different phenotypes in response to the environments they experience. Alternatively, an individual's phenotype may be under the control of its parents, usually the mother (transgenerational or indirect plasticity), so that mother's genotype determines the phenotype produced by a given genotype of her offspring. Under what conditions does plasticity evolve to have intragenerational as opposed to transgenerational genetic control? To explore this question, we present a population genetic model for the evolution of transgenerational and intragenerational plasticity. We hypothesize that the capacity for plasticity incurs a fitness cost, which is borne either by the individual developing the plastic phenotype or by its mother. We also hypothesize that individuals are imperfect predictors of future environments and their capacity for plasticity can lead them occasionally to make a low‐fitness phenotype for a particular environment. When the cost, benefit and error parameters are equal, we show that there is no evolutionary advantage to intragenerational over transgenerational plasticity, although the rate of evolution of transgenerational plasticity is half the rate for intragenerational plasticity, as predicted by theory on indirect genetic effects. We find that transgenerational plasticity evolves when mothers are better predictors of future environments than offspring or when the fitness cost of the capacity for plasticity is more readily borne by a mother than by her developing offspring. We discuss different natural systems with either direct intragenerational plasticity or indirect transgenerational plasticity and find a pattern qualitatively in accord with the predictions of our model.

Cycloalexy was coined by Vasconcellos-Neto and Jolivet in 1988 and further defined by Jolivet and collaborators in 1990 in reference to a specific type of circular defence. The term has been applied to numerous organisms, including adult insects, nymphs, and even vertebrates, but has lost precision with the accumulation of anecdotal reports not addressing key elements of the behaviour as first defined. We review the literature and propose three criteria that are sufficient and necessary to define the behaviour: (1) individuals form a circle; (2) defensive attributes of the individuals are positioned on the periphery of the circle, and as a result, the periphery of the circle uniformly contains either heads or abdomens; (3) animals preemptively adopt the circle as a resting formation, meaning it is not necessary to observe predation. When these considerations are taken into account, cycloalexy appears less common in nature than the literature suggests. We argue that unequivocal cases of cycloalexy have been found only in sawflies (Tenthredinoidea: Pergidae, Argidae), leaf beetles (Chrysolemidae: Galerucinae, Cassidinae, Chrysomelinae, Criocerinae), weevils (Curculionidae:Phelypera distigma), and midges (Diptera: Ceratopogonidae,Forcipomyia). Reports of cycloalexy in caterpillars (Saturniidae: Hemileucinae:Lonomia, Papilionidae) require further documentation. We report one new case of cycloalexy in thrips (Thysanoptera) and question reports of cycloalexic behaviour in other taxa.