Phenology of the semiaquatic caterpillar Paracles klagesi and its response to environmental changes

Abstract

Phenological patterns can arise as a response to seasonal variation and are closely related to rain regimes and temperature. Organisms living in the water/atmosphere interface receive stimuli from both environments and require adaptations to survive. Paracles klagesi (Rothschild, 1910) is a semiaquatic caterpillar with a terrestrial adult form found in streams in a Brazilian savannah. We hypothesized that the semiaquatic larvae of this species respond to atmospheric environmental changes in rainfall and temperature by synchronizing their development throughout the year, with the highest abundance during the dry season and the lowest in the rainy season. We followed a caterpillar population for 1 year, counted and measured individuals every 15 days and obtained monthly average temperature and rainfall data. Currently, there is no description of P. klagesi instars; therefore, we categorized them into six size classes and a pupal stage. Since phenological and physiological responses are complex and may not be perceived at the time of the stimulus, we used a Pearson's correlation test with a time lag of up to 3 months to investigate the influence of rainfall and temperature. The caterpillars showed synchronized development over time, supporting our first hypothesis. The time-lag analysis identified an immediate inverse relationship between caterpillar abundance and monthly rainfall, while the temperature had a delayed positive relationship with pupae of 3 months. Our results showed that P. klagesi synchronized its development with time and, as a semiaquatic insect, used atmospheric cues for pupae to complete its development. This is the first study providing information about phenology and the role of temperature and rainfall in the development of a semiaquatic lepidopteran. We believe that unusual strategies by insects may provide data for understanding how evolutionary forces influence adaptations as insects colonize new environments.