Bivoltine

Definition

Having two generations or broods per year. A bivoltine life cycle involves adults emerging and reproducing in two discrete pulses, typically in spring and summer, with the second generation either completing development before winter or entering diapause as immature stages. This strategy contrasts with univoltine (one generation) and multivoltine (three or more generations) patterns, and represents an intermediate response to season length and thermal accumulation.

Etymology

From Latin bi- (two) + voltinism (from Italian volta, turn or time, referring to broods per year)

Example

The speckled wood butterfly Pararge aegeria exhibits facultative bivoltinism: populations in warm southern regions reliably produce two broods, while northern populations may be univoltine or show mixed strategies depending on spring temperature and larval development rate.

Synonyms

• digenic
• digenetic (seasonal context, rare)

Related Terms

• voltinism
• Univoltine
• multivoltine
• semivoltine
• partial bivoltine
• facultative voltinism
• provenance
• thermal time
• degree-days

Usage Notes

Bivoltine is strictly a phenological descriptor, not a taxonomic category. Some authors distinguish 'facultative bivoltine' (plastic response to conditions) from 'obligate bivoltine' (genetically fixed). The term is most common in lepidopteran and coleopteran literature but applies broadly to seasonal insects. In sericulture, bivoltine silkworm races produce two cocoon crops annually, contrasting with univoltine (one crop) and polyvoltine (continuous breeding) strains. When describing populations with overlapping generations or unclear brood structure, 'partially bivoltine' or 'bivoltine tendency' may be preferred.