What was done
Larvae of the satyrid butterfly (Coenonympha pamphilus) were raised in seminatural, undisturbed calcareous grassland plots exposed to atmospheric CO2 concentrations of 370 and 600 ppm for five growing seasons to study the effects of elevated CO2 on growth performance in this herbivorous insect.

What was learned
The elevated atmospheric CO2 concentration increased foliar concentrations of total nonstructural carbohydrates and condensed tannins in the grassland plants.  In what is often considered a negative impact, however, it decreased foliar nitrogen concentrations.  Nevertheless, this phenomenon had no discernible negative impact on butterfly growth and performance characteristics.  Larval developmental time, for example, was not affected by elevated CO2, nor was adult dry mass.  In fact, the elevated CO2 increased lipid concentrations in adult male butterflies by nearly 14%, while it marginally increased the number of eggs in female butterflies.

What it means
As the atmospheric CO2 concentration increases, larvae of the satyrid butterfly likely will not be negatively affected by feeding upon grassland plants that may exhibit reduced foliar nitrogen concentrations.  Indeed, increases in the air's CO2 concentration may actually increase the fitness of this butterfly species.  Adult males exposed to elevated CO2, for example, exhibited greater body concentrations of lipids, which compounds are used as energy resources in these and other butterflies.  In addition, elevated CO2 increased egg numbers in females, which also suggests an increase in fitness.  Thus, this species - and perhaps others - will likely exhibit positive responses to future increases in the air's CO2 concentration.