| Elevational adaptation in voltinism

Development rate of embryos of dark bush‐crickets reared in a common laboratory environment increased with elevation of parental population. In lowland populations it took longer to hatch after being exposed to warm temperatures, than in populations from highlands. This suggests the genetically underpinned local adaptation of this insect to a shorter growing season in a harsher mountain environment.

| Reproductive interference of sister bush-crickets

Coexistence of species is very rare locally with mostly mutually exclusive distribution patterns, resulting in a mosaic pattern of sympatry. Experimental trials revealed 8% interspecific copulations. Because females also obtain required nutrition from a heterospecific spermatophylax, we suggest that this reproductive interference result in the competitive exclusion of the inferior species from the area.

| Size‐dependent mating pattern

Frequency of within‐pair copulations was positively associated with the body size of both mated individuals with significant interaction between sexes. Larger individuals also showed a higher degree of polygamy. This suggests that body size of nuptial gift‐giving insect species may be an important sexual trait according to which both sexes choose their optimal mating partner.

| Environmentally driven variability in polyandry

Interactions between the body size with environmental factors revealed that larger females originating from the highland population and larger females reared in cold treatment copulated more often than smaller ones, whereas females’ size did not affect copulation frequency in the lowland population or in warm treatment. It suggests stronger competition among females in harsher environmental conditions.

| Ejaculate volume and mating rate

The results based on field-caught individuals suggested that there were statistically significant negative association between smallest and mean spermatodose volume, respectively, and number of copulations in studied nuptial gift-giving bush-cricket species. This is in accordance with interspecific associations between ejaculate size and polyandry.

| Polyandry and latitude

Along a latitudinal gradient in northern Europe, the degree of polyandry was generally increasing at higher latitudes. The field-based results suggested that there were potentially interesting interactions between environment, life-history traits, and patterns of polyandry in nuptial-gift-giving insect species.