Common walnut, due to decorative habit of its crown, is a frequently growing tree in Lublin’s parks and gardens. Its presence in the town landscape provokes deeper analysis of the fauna occurring on it. The aim of this paper was to trace the changes in numerical force with reference to the weather conditions system, as well as to establish the bionomics of Panaphis juglandis (Goeze) occupying the trees of Juglans regia L. Studies were conducted on common walnut (Juglans regia L.) in Lublin in 2006–2008. Three locations were designed for observation: garden (A), park (B) and street-side (C). Numerical strength and bionomics of P. juglandis were determined. The greatest number of aphids was reported in the year 2007 in the park location. The course of weather conditions significantly affected the terms of spring and autumn presence of aphids. Warm spring with not very intense precipitation enhanced the development of P. juglandis. However, torrential rains and air temperatures exceeding 30ºC in summer limited the population dynamics of this aphid. In the developmental cycle the appearance of subsequent generations was observed from family founders through virginoparous females to sexual generation. Studies on female fecundity were performed. In all the study years the highest mean fecundity was that of the family founders, and the lowest was found in the females of sexual generation. The most fecunde virginoparous females (68.4 larvae · female^-1) were observed in spring 2006 in the street location. Observations were also undertaken, which concerned determining the place and term of aphid occurrence, as well as the number of eggs on lignified sprouts of Juglans regia L. The highest number of eggs was reported in 2008 in the park location.

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