Both Scymnus syriacus Mars. and Scymnus levaillanti Muls. are aphidophagous coccinellids. In the laboratory they consumed and successfully reproduced on several species of aphids. Larvae suck the prey contents from aphid appendages, while adults consume the whole aphid, except for parts of the appendages. Extra-oral digestion is practiced during feeding. The mean number of aphids consumed by the larval stage of S. syriacus when reared at 25°C was 95, and 130 aphids at 30°C. For S. levaillanti it was 125 and 139 aphids at 25°C and 30°C, respectively. The mean number of eggs deposited daily by S. syriacus for the first three weeks of adult life was 19.5, with a range of 3-30 eggs at 25°C. Longevity of adults ranged from 3 to 4 months at 25°C and 2.5-3 months at 30°C.
The development of a B-biotype Bemisia tabaci Italian colony was studied on bean at 9 constant temperatures (15, 16, 17, 20, 23, 26, 29, 32, 35°C). The developmental time from egg-to-adult varied from 70 days at 16°C to 22 at 26°C and higher temperatures. A thermal requirement for egg-to-adult development of 307 day-degrees was calculated, based on a lower developmental threshold of 11.53°C. The survival of egg, nymph and adult whiteflies was investigated at 0, 2, 4, and 6°C on broad bean for periods of 1-8 days. The adult was the most cold-sensitive stage, while the egg and nymph showed a similar level of cold resistance. The effect of sub-lethal cold stress of 4-8 days at 4°C on eggs and nymphs was studied. After exposure to low temperatures, whiteflies needed longer developmental times, from 5 to 8 days more. The presence of B. tabaci under outdoor conditions in Italy was investigated with field surveys and correlated with climatic data; the whitefly species was found in open field conditions only south of the 41° parallel, in areas characterised by less than 5 frost days per winter and by annual mean temperatures >16°C.
Life table data of natural enemies are often used to understand their population dynamics and estimate their potential role in the biological control of pests. Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae) is an important pest of several crops and its intrinsic rate of population increase (rm) is 0.282 at 22°C. The life table parameters (immature mortality, developmental time, sex ratio of emerging adults, fecundity and longevity) of Praon volucre (Haliday) (Hymenoptera: Braconidae: Aphidiinae) parasitizing M. euphorbiae were estimated in a climatic chamber at 22 ± 1°C, RH 70 ± 10% and 12 h photophase. Immature mortality was 8.2%, developmental time of males and females was 13.9 and 14.4 days, respectively, and the sex ratio was 0.55 (= fraction of females). Parasitoid fecundity was 504 eggs and longevity 11 days. The net rate of reproduction (R0) was 207.5 females and the intrinsic rate of population increase (rm) 0.281 females/female/day. The time for doubling the population (TD) was 2.45 weeks. P. volucre has a population growth rate similar to that of its host M. euphorbiae and might therefore be a good candidate for the biological control of this aphid. and Juracy Caldeira Lins jr., Vanda Helena Paes Bueno, Diego Bastos Silva, Marcus Vinicius Sampaio, Joop C. van Lenteren.