# Voltinism

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Number of generations or broods of an organism per year

A *[Lycaena phlaeas](/source/Lycaena_phlaeas)* (small [copper butterfly](/source/Lycaeninae)) perching on a plant

**Voltinism** is a term used in [biology](/source/Biology) to indicate the number of broods or generations that an [organism](/source/Organism) has each year. The term is most often applied to [insects](/source/Insect), and is particularly in use in [sericulture](/source/Sericulture), in which [silkworm](/source/Silkworm) varieties vary in their voltinism.

The following adjectives describe organisms:

- **Univoltine** (**monovoltine**) – having one brood or generation per year

- **Bivoltine** (**divoltine**) – having two broods or generations per year

- **Trivoltine** – having three broods or generations per year

- **Multivoltine** (**polyvoltine**) – having more than two broods or generations per year

- **Semivoltine** – with two meanings:

- - being less than univoltine; having a brood or generation less often than once per year - having a [generation time](/source/Generation_time) that lasts more than one year.[1]

## Examples

The [speckled wood butterfly](/source/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](/source/Pupation), enter [diapause](/source/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**[2] – 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](/source/Parnassius_smintheus) and the [high brown fritillary](/source/High_brown_fritillary) are more examples of univoltine butterfly species.[2][3]

The bee species *[Macrotera portalis](/source/Macrotera_portalis)* is bivoltine, and is estimated to have about 2 or 3 broods annually. During winter, individuals remain in diapause, in their pharate or prepupal stage. This diapause stage continues until metamorphosis in the next spring or summer, whereupon the bees emerge as adults.[4] Another example of a bivoltine species is *[Cyclosa turbinata](/source/Cyclosa_turbinata)* which is known to reproduce once in the late spring and once again in the fall.

The [Dawson's burrowing bee](/source/Amegilla_dawsoni) is an example of a **univoltine** insect of the order [Hymenoptera](/source/Hymenoptera). The brood of one winter will remain dormant underground until the following winter, and then will surface from their burrows to mate once, and establish new nests.

### Partial voltinism

The term **partial voltinism** is used to refer to two different (but not necessarily exclusive) situations:

- An organism wherein generations overlap in time, and so are not completely reproductively isolated. For example, in bees of the subfamily [Halictinae](/source/Halictinae), one generation is produced in the early summer and one in the late summer, but males produced in the early summer may also [mate](/source/Mating) in the late summer.[5]

- (More commonly) a population where the voltinism is mixed, because of genetic variation (e.g., in the [hybrid zone](/source/Hybrid_zone) between a univoltine and a bivoltine area) and/or because environmental stimuli do not induce bivoltinism in all individuals (or across all years). For example, far-northern populations of the [green-veined white](/source/Green-veined_white) butterfly *Pieris napi* are mostly univoltine, but some individuals may avert [diapause](/source/Diapause) and produce an additional generation under warm conditions.[6]

## Evolution

The number of breeding cycles in a year is under genetic control in many species[7] and they are evolved in response to the environment. Many [phytophagous](/source/Phytophagous) species that are dependent on seasonal plant resources are univoltine. Some such species have the ability to diapause for a large part of the year, typically during a cold winter.[8] Others that bore in wood or other low-grade, but plentiful, food material may spend nearly the entire year feeding, with only brief pupal, adult and egg stages to complete a univoltine life cycle. Yet other species that live in tropical regions with little seasonality may be highly multivoltine, with several generations feeding on constantly growing vegetation (such as some species of [Saturniidae](/source/Saturniidae)), or continually renewed detritus, such as *[Drosophila](/source/Drosophila)* and many other genera of flies with a life cycle of just a week or two.[9]

## See also

- [Semelparity and iteroparity](/source/Semelparity_and_iteroparity)

## References

1. **[^](#cite_ref-1)** Resh, Vincent H.; Carde, Ring T., eds. (2009). ["Glossary"](https://ibimm.org.br/wp-content/uploads/2017/05/enciclopedia-de-insetos-ingles.pdf) (PDF). *Encyclopedia of Insects* (2nd ed.). [Academic Press](/source/Academic_Press)/[Elsevier](/source/Elsevier). p. 1088.

1. ^ [***a***](#cite_ref-Aalberg_2-0) [***b***](#cite_ref-Aalberg_2-1) Aalberg Haugen IM, Berger D, and Gotthard K. 2012. The evolution of alternative developmental pathways: footprints of selection on life-history traits in a butterfly. 12pp. Journal of Evolutionary Biology, 25:7, Available online: [\[1\]](http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2012.02525.x/full)

1. **[^](#cite_ref-3)** Shepard, Jon; Guppy, Crispin (2011). [*Butterflies of British Columbia: Including Western Alberta, Southern Yukon, the Alaska Panhandle, Washington, Northern Oregon, Northern Idaho, and Northwestern Montana*](https://books.google.com/books?id=il6rJ7glHNQC&q=parnassius+smintheus&pg=PA53). UBC Press. [ISBN](/source/ISBN_(identifier)) [9780774844376](https://en.wikipedia.org/wiki/Special:BookSources/9780774844376).

1. **[^](#cite_ref-museum_4-0)** Buchmann, Stephen L. ["Bees"](https://desertmuseum.org/books/nhsd_bees.php?print=y), *[Bees](/source/Bees)*, Retrieved on 15 October 2015.

1. **[^](#cite_ref-Seger_5-0)** Seger J. 1983. Partial bivoltinism may cause alternating sex-ratio biases that favor eusociality. 4pp. Nature, 301:59-62, Available online: [\[2\]](http://www.nature.com/nature/journal/v301/n5895/abs/301059a0.html)

1. **[^](#cite_ref-Kivelä_6-0)** Kivelä SM, Svensson B, Tiwe A, and Gotthard K. 2015. Thermal plasticity of growth and development varies adaptively among alternative developmental pathways. 13pp. Evolution, 69:9, Available online: [\[3\]](http://onlinelibrary.wiley.com/doi/10.1111/evo.12734/full)

1. **[^](#cite_ref-7)** Coates BS, Sumerford DV, and Hellmich RL. 2004. Geographic and voltinism differentiation among North American *Ostrinia nubilalis* (European corn borer) mitochondrial cytochrome c oxidase haplotypes. 9pp. Journal of Insect Science, 4:35, Available online: [\[4\]](http://insectscience.org/4.35)

1. **[^](#cite_ref-8)** Hunter, M.D. and J.N. McNeil. 1997 Host-plant quality influences diapause and voltinism in a polyphagous insect herbivore. Ecology 78: 977-986. [\[5\]](https://wayback.archive-it.org/all/20070417171443/http://www.arches.uga.edu/~mdhunter/publications/Ecology_97_Hunter&McNeil.pdf)

1. **[^](#cite_ref-Schowalter2011_9-0)** Timothy Duane Schowalter (2011). [*Insect Ecology: An Ecosystem Approach*](https://books.google.com/books?id=2KzokTLIysQC&pg=PA159). Academic Press. p. 159. [ISBN](/source/ISBN_(identifier)) [978-0-12-381351-0](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-381351-0).

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Adapted from the Wikipedia article [Voltinism](https://en.wikipedia.org/wiki/Voltinism) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Voltinism?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.