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Nymphal development and food consumption ofAtractotomus mali (Meyer-Diir) (Hemiptera:Miridae), reared on Aphis pomi (DeGeer) and Psyllamali SchmidbergerNINA JONSSONJonsson, N. 1987. Nymphal development and food consumption ofAtractotomus ma/i(Meyer-Diir) (Hemiptera: Miridae), reared on Aphis pomi (DeGeer) and Psy/la ma/iSchmidberger. Fauna norv. Ser. B, 34, 22-28.Food consumption and the duration of nymphal development of Atractotomus maliwere tested by rearing A. mali on apple leaves, the aphide Aphis pomi and the psyllidePsylla mali. Few A. ma/i nymphs developed when fed on only apple leaves. 3.8% ofthem survived from 2 nymphal stage until adulthood. A. mali nymphs consumed moreanimal food at 20°C that at 15°C, and their consumption of A. pomi was higher thanthat of P. mali nymphs. At a temperature of 20°C, A. mali nymphs in stages 2-5consumed 87 A. pomi or a dry-weight 3.7 mg, and 40 P. mali with a dry-weight of 2.1mg. Corresponding figures at 15°C were 110 A. pomi or 5.0 mg, and 41 P. mali and 2.3mg. The duration of A. mali development from nymphal stages 2 to 5 was 11.6 days at20°C when fed on P. mali, and 13.0 days when fed on A. pomi. Figures at 15°C were22.6 days and 28.8 days, respectively. Adult A. ma/iconsumed more P. mali in nymphalstages 4-5 than they consumed adults. During a 15 day period at 20°C, 26.2 P. malinymphs with a dry-weight of 4.60 mg and 11 P. ma/i adults with a dry-weight of 1.90mg were consumed. At 15°C, 15.8 P. malinymphs (dry-weight 2.80 mg) and 4.7 P. maliadults (dry-weight 0.83 mg) were consumed. A single adult A. mali was capable tocontrolling populations of 50 A. pomi individuals in an apple tree.Nina Jonsson 1 , University of Oslo, Department of Zoology, Section of Zoology, P.O.Box 1050, Blindern, N-0316 Oslo 3, Norway.INTRODUCTIONA tractotomus mali is a common heteropteranin Norwegian apple orchards (Austreng &S0mme 1980, SkAnland 1981 a, J onsson1983a). Existing literature gives contradictoryinformations concerning the food of thisspecies. Collyer (1953), Sandford (1964) andLord (1971) maintained that A. mali nymphscan survive and develop to adults in the ab­sence of animal food, whereas Leonard(1965), Strawinski (1964) and MacPhee(1976) claimed that A. mali is mainly zoo­phagous, or feeds on a combination ofanimaland plant foods. Thus far, few quantitativestudies on food consumption by A. malinymphs and adults, and the effects of diffe-rent food items on nymphal development atvarious temperatures have been published.Therefore I tested the duration of nymphaldevelopment in association with A. mali consumptionQat two different tern peratures (15°Cand 20 C), when fed on prey species Aphispomi and Psylla mali placed on apple leaves,and when fed only on apple leaves. I comparedthe consumption of adult A. mali rearedon P. mali nymphs, with that of P. maliadults. The potential size of A. pomi populationswtich may be controlled by A. maliplaced in apple trees was also examined.METHODSThe laboratory experiments were conductedat two different temperatures (15± I QC and1) Present address: Directorate for Nature Mana­ 20±I 0c) between 6 May-5 August 1980.gement, Research Division, Tungasletta 2, Relative humidity during the experimentsN-7004 Trondheim, Norway. was 60±5%, the illumination was 941ux. The22Fauna nOrl/. Ser. B, 34: 22-28. Oslo 1987.