Tiny insects against the weather-flight and foraging patterns of Frankliniella schultzei (Thripidae) not altered by onset of rainfall

To survive in nature, organisms may need to take direct action to mitigate specific dangers from their environmental surroundings. Tiny flying insects are thought to be at particular risk from rainfall that would be of negligible concern to larger animals. The study species Frankliniella schultzei is a thrips that inhabits flowers and feeds mostly on petal tissue and pollen. While found to respond in the laboratory to decreases in atmospheric pressure associated with cyclonic conditions (rather than merely heavy rainfall), their responses to conditions preceding rainfall have not been tested in the field. Initial field sampling investigated the relationship between floral development and sites at which male, female, and larval thrips were generally present on sunny days. We then designed a sampling strategy to test if these thrips can anticipate imminent rainfall or storms and so seek shelter deep within flowers, by sampling host flowers (in sections) on multiple days with different weather conditions. Sticky traps were used to intercept thrips in flight, thus providing a measure of flight behavior across different days. The initial sampling found adult thrips primarily at the petal apex of anthesis-stage flowers where pollen is distributed. We subsequently found that rainfall, atmospheric pressure change, temperature, humidity and wind had no effect on flight behavior of F. schultzei, or on their positions within flowers. These findings suggest rainfall is not a serious hazard for them. Perhaps thrips can survive raindrop collisions during flight, as impacts with water droplets are not expected to break the surface tension