در مزارع برنج استان گيلان Andrallus Spinidens F. شكل شناسي خارجي زيست شناسي و توزيع فضايي سن شكارگر

Morphology, biology and spatial distribution of the rice field predator, Andrallus spinidens (Hem: Pentatomidae) in rice field in Guilan Province

Andrallus spinidens F. is a predator on a wide range of insect pests of economic important pests in fields like Naranga aenescens and chilo suppressalis. Biology, seasonal fluctuation and spatial distribution of Andrallus spinidens F. studied under laboratory (at temperature of 23.18 ± 1 and relative humidity of 92.57 ± 2% ) and field conditions by twice a week sampling using a sweep net. To study spatial distribution, sweep net and direct count methods were used to take sampling. This two method were also compared. The incubation period was, 9+_ 0.5 days. Eggs were light brown in colour and were laid in a cluster. The nymphal developmental time feeding on Naranga aenescens and chilo suppressalis larvae were 24 ± 0.46 and 26.33 ± 0.46 days, respectively. There were five nymphal instars. Adult insects are yellowish brown male and longevity was 9.83 and 16.3 days, respectively. Mating took 160± 14.73 minutes, average number of eggs laid by a female was 241. 66± 30.40. Nymphs and adults feed on prey larvae and such their body fluids. A.spinidens overwintered as a adult and there was 3 generations in a year. Spatial distribution of A.spinidens population was determined by Taylorʹs Power Law. Nymphs were aggregated on different rice Varieties. Aggregation indices (b) for nymphs were 2.76, 2.2 and 3.26 on Binam and Sepidroud (sweep net) and Binam (direct count), respectively. Aggregation index for adult insect on Binam (Sweep net) was 1.26 which is an aggregated distribution. These experiment showed that a sweep net sampling method was better to estimate Predator population.