Abstract
Despite the prominent role that insects play in ecological food webs, the reduced availability of long term data sets on insect phenology compared to that available for higher tropic groups, such as birds and plants, have led to their being largely underrepresented in phenological research in North America. This crucial missing link has limited the understanding of the community level effects caused by climate change. In this study we examined the impact of spring temperature and precipitation on the flight dates of 10 short-lived species of Massachusetts butterflies from two genera within the Lycaenidae family. We obtained records of butterflies in flight using historic data (pre-1986) mainly obtained from museum collections and contemporary data (1986-2009) from the Massachusetts Butterfly Club, a citizen science group. We located over 5,000 records of Lycaenidae butterflies in flight. We analyzed the data using linear regression models with sighting date as the response variable and temperature, precipitation, geographic location, and year as predictor variables. Temperature explained more variation in flight date than the other predictors, and all species had significant earlier flight times in warmer years. The mean advancement in sighting date was 2.9 days/°C. Precipitation was not significantly correlated to the date of sighting in most of the species. During our study period there was no significant change in sighting dates over the entire study period (1893-2009) for most species, but half of the species are flying significantly earlier in more recent years (1986-2009). These results suggest that butterflies do respond to climatic variation, and are likely to be affected by climate change. The response rate to temperature of these butterfly species is similar to the rate of advancement of plant flowering in the same area. This study also demonstrates the successful use of museum specimens and citizen science data for climate change studies of insects.