Effect of gamma rays on adult flight agility and distribution of Old World screwworm, Chrysomya bezziana, irradiated at the pupal stage

The larvae of Old World screwworm, Chrysomya bezziana were reared on a meat-based diet containing: lean minced beef (54%), fresh blood (15% containing 10% EDTA), water (30%) and formalin (0.2%). The developed pupae were separated in plastic containers containing vermiculite or corncob grits and incubated for adult emergence under 28 deg. C and 70% relative humidity. The emerged adults were transferred into the adult cages (made from cloth tissue, black or white), provided with water, honey and sugar. Radiation Treatments: At the 5th day of female age, egging dishes were prepared from ground meat, clotted blood or pieces of liver, oviposition stimulants deg. Cntaining spent medium immersed inside the dish. All the contents were warmed on a hotplate to 37 - 39 deg. C. The egging dishes were provided daily for two hours inside the cage for egg deposition. Egg masses and newly hatched larvae were taken for establishing the laboratory colony. The average larval period was 6.8 days, rate of pupation 93.2%, pupal period 7.6 days and rate of pupal development 79%. Pupae at 2-5 days were irradiated with a Gammacell 220. Percentage pupal development to adults decreased from 82% for non-irradiated pupae, to 3%, 12%, 29% and 22% for pupae irradiated with a dose of 90 Gy at 2, 3, 4 and 6 days age. The lifespan of adults emerged from irradiated pupae decreased with increasing gamma dose. Sixty Gy or less did not have an effect on the ovarian development. No egg hatch resulted from the crosses between treatments of 60 to 90 Gy. Egg hatch was observed only in normal adult crosses or in normal females mated with males emerged from 45 Gy irradiated pupae. Flight Agility Test: A small cylinder was made from transparent paper (10 cm long X 10 cm diameter) and lined by baby powder to avoid adults walking out of the cylinder. A group of adults (newly emerged from irradiated pupae) were left inside each cylinder under appropriate temperature and humidity. Adults with flight ability escaped from the cylinder, and were caught by sticky papers hung inside the room. The Flight Agility Index (F.A.I.) was calculated by using an equation