Voltinism

Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is most often applied to insects, and is particularly in use in sericulture, where silkworm varieties vary in their voltinism. Univoltine (monovoltine) – (adjective) referring to organisms having one brood or generation per year Bivoltine (divoltine) – (adjective) referring to organisms having two broods or generations per year Trivoltine – (adjective) referring to organisms having three broods or generations per year Multivoltine (polyvoltine) – (adjective) referring to organisms having more than two broods or generations per year Semivoltine – There are two meanings: (biology) Less than univoltine; having a brood or generation less often than once per year or (adjective) referring to organisms whose generation time is more than one year. The speckled wood butterfly is univoltine in the northern part of its range, e.g. northern Scandinavia. Adults emerge in late spring, mate, and die shortly after laying eggs; their offspring will grow until pupation, enter diapause in anticipation of the winter, and emerge as adults the following year – thus resulting in a single generation of butterflies per year. In southern Scandinavia, the same species is bivoltine – here, the offspring of spring-emerging adults will develop directly into adults during the summer, mate, and die. Their offspring in turn constitute a second generation, which is the generation that will enter winter diapause and emerge as adults (and mate) in the spring of the following year. This results in a pattern of one short-lived generation (c. 2–3 months) that breeds during the summer, and one long-lived generation (c. 9–10 months) that diapauses through the winter and breeds in the spring. The Rocky Mountain parnassian and the High brown fritillary are more examples of univoltine butterfly species. The bee species Macrotera portalis is bivoltine, and is estimated to have about 2 or 3 broods annually.