Cost to the cavity-nest ant Temnothorax crassispinus (Hymenoptera: Formicidae) of overwintering aboveground

Abstract

Abstract. Most species of ants inhabiting the temperate zone overwinter underground, whereas those of the genus Temnothorax remain in nests aboveground. I studied the cost of aboveground overwintering. Workers of Temnothorax crassispinus survived in higher numbers (median = 88%) in artificial nests experimentally buried at a depth of 5 cm than those in nests on the surface (48%) of the soil. The results support the hypothesis that overwintering aboveground could be a consequence of a limited supply of nests and/or the advantage of being able to respond quickly to warm temperatures in spring.

Size-related mortality during overwintering in cavity-nesting ant colonies (Hymenoptera: Formicidae)

“…The mortality of Temnothorax ants overwintering in nests at ground level may be high (Herbers & Johnson, 2007;Mitrus, 2013). However, nest sites on the ground differ in different localities: for example some of them may be under leaves whereas others are on bare ground and more exposed to frost.…”

“…This study shows that the fusion of colonies (resulting in an increase in the number of workers) may have an effect on their survival during some winters; mostly when frost is severe and there is lack of snow cover or such cover is thick. During this study I collected queen less colonies and those with only one queen, but in previous autumns I found colonies with several, even seven, queens (Mitrus, 2013(Mitrus, , 2015a. It would be interesting to check if in areas where there is a higher probability of the nests being on bare exposed ground and more exposed to extreme temperatures, whether the fusion of colonies is more frequent.…”

“…Therefore, during winter, ants in such sites may be exposed to extreme temperatures. Earlier studies indicate that the mortality of the ant Temnothorax during winter may be high (Herbers & Johnson, 2007;Mitrus, 2013), however, when winter is mild, the survival rate might be very high, and even larval development may be completed (Mitrus, 2015a).…”

The cavity-nest ant Temnothorax crassispinus prefers larger nests

“…In late summer and autumn, T. crassispinus ant colonies may consist of over 300 workers (Mitrus, 2013;and unpubl. data).…”

Effects of overwintering temperature on the survival of the black garden ant (Lasius niger)

“…Ants typically overwinter in their perennial colonies at different depths, some with a brood and others without one (Tauber et al, 1986). The layer of soil where ants overwinter can vary from 0 cm to 1.5 m depending on the species and the location where the nest is built (Berman et al, 2010;Mitrus, 2013). The greater the depth at which ants overwinter, the less likely it is that they will encounter extreme or variable temperature regimes during overwintering period.…”