Most studies of responses of insects to elevated carbon dioxide have been m
ade using short-term exposures to treated food plants and have involved mea
surements of responses in growth, reproduction, food consumption and effici
encies of conversion at specific stages in the life cycle. These will be re
viewed in the light of longer-term studies recently published where whole g
enerations have been reared in chambers with simultaneous treatment of plan
ts and where insects have been free to select their food and microenvironme
nt. Factors such as seasonal change in plants, choice of food plant, mode o
f feeding, timing of exposure, temperature, the role of natural enemies are
considered and the whole placed in the context of other aspects of climate
change.
It is concluded that in studies to date, the only feeding guild in which so
me species have shown increases in population density in elevated carbon di
oxide are the phloem feeders. Chewing insects (both free-living,and mining)
generally have shown no change or reduction in abundance, though relative
abundance may be greatly affected. Compensatory feeding is common in these
groups.