Life cycles of some insects adapt well to a changing climate. Others, not so much. 

As insect populations decrease worldwide in what some have called an “insect apocalypse,” biologists are desperate to determine how the six-legged creatures are responding to a warming world and to predict the long-term winners and losers.A new study of Colorado grasshoppers shows that, while the answers are complicated, biologists have much of the knowledge they need to make these predictions and prepare for the consequences.The findings, published Jan. 30 in the journal PLOS Biology, come thanks to the serendipitous discovery of 13,000 grasshoppers all collected from the same Colorado mountain site between 1958 and 1960 by a biologist at the University of Colorado Boulder (CU Boulder). After that scientist’s untimely death in 1973, the collection was rescued by his son and donated to the CU Museum, where it languished until 2005, when César Nufio, then a postdoctoral fellow, rediscovered it. Nufio set about curating the collection and initiated a resurvey of the same sites to collect more grasshoppers.The newly collected insects allowed Nufio and his colleagues — Caroline Williams of the University of California, Berkeley, Lauren Buckley of the University of Washington in Seattle and postdoctoral fellow Monica Sheffer, who has an appointment at both institutions — to assess the impact of climate change over the past 65 years on the sizes of six species of grasshopper. Because insects are cold-blooded and don’t generate their own heat, their body temperatures and rates of development and growth are more sensitive to warming in the environment.A portion of the 13,000 grasshoppers collected by the late Gordon Alexander of CU Boulder. The 65-year-old grasshoppers were compared with contemporary insects to assess the effect of climate change on their size and range.César Nufio
Despite much speculation that animals will decrease in size to lessen heat stress as the climate warms, the biologists found that some of the grasshopper species actually got larger over the decades, taking advantage of an earlier spring to fatten up on greenery. This worked only for species that overwinter as juveniles — a stage called nymphal diapause — and thus can get a head start on chowing down in the spring. Species that hatch in the spring from eggs laid in the fall — the egg diapausers — did not have this advantage and became smaller over the years, likely as a result of vegetation drying up earlier.“This research emphasizes that there will certainly be species that are winners and losers, but subgroups within those species populations, depending on their ecological or environmental context, will have different responses,” Sheffer said.The authors of the new study predicted much of this based on the life cycles of the grasshoppers and the environmental conditions at the site.“We sat down and looked at all that was known about the system, such as elevational gradients and how that should modify responses and how different grasshoppers might