The movement of fly (Diptera) larvae within a feeding aggregation

Abstract

Dipteran larvae from a number of families feed in aggregations. Rotation of blow fly (Diptera: Calliphoridae) larvae within an aggregation has been reported anecdotally many times. However, there is a lack of quantitative data on such larval movement, which is necessary to better understand the advantage of this gregarious behaviour. A recent development in tagging methods provided an opportunity to address this gap in knowledge. In 15 aggregations of 500 Lucilia sericata (Meigen) (Diptera: Calliphoridae) larvae, the location of four-tagged individuals was recorded at 10-minute intervals. All larvae were seen to rotate, alternating between the periphery and within. There was much variation in the relative proportions that larvae were seen in these two locations among aggregations (?2=78.4, df=58, P=0.038), perhaps as a result of differences in mass shape and, therefore, surface area: volume ratio. There were also differences between larvae within aggregations (?2=25.6, df=14, P=0.029), which may give rise to differences in development rate, perhaps as a result of intraspecific competition. Further work would be required to verify this competition, and to establish whether the limited resource is temperature, food, oxygen, or some other requirement.