DETERMINATION OF INSTAR FOR THE WINDOW GNAT SYLVICOLA-FENESTRALIS (DIPTERA, ANISOPODIDAE)

The Window Gnat Sylvicola fenestralis is a major nuisance fly inhabiti ng the biological filters of sewage treatment works. Analysis of measu rements of head capsule width, head capsule length and larval body len gth of 303 laboratory hatched and field collected larvae, established that this species possesses four larval instars. The size range of eac h instar for the three parameters was determined by plotting cumulativ e frequency against sample category on probability paper; the inflexio n curve method. The growth rate between instars was shown to fit Dyar' s rule for all three parameters. The efficacy of many insecticides dep ends on accurate targeting against the most susceptible stage of the i nsect life cycle. Hence a more detailed knowledge of the instars of S. fenestralis will allow for the most effective control of this nuisanc e species. Copyright (C) 1996 Elsevier Science Ltd