Résumé :
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In years 1952-1956 studies were carried on some problems of biology and ecology of Adelphocoris lineolatus Goeze. In these studies the following moments were investigated : 1. the location of A. lineolatus Goeze eggs in alfalfa plants and weeds, 2. the eggs laying period, 3. the duration of egg stage, the larval development and the period of appearance of adults, 4. the life time and the number of eggs laid by a female, 5. the number of broods, 6. the damage done by A. mineolatus Goeze on the alfalfa in the field conditions, 7. the horizontal distribution of A. lineolatus Goeze on the alfalfa fields, 8. the changes in quantity on the same fields in the successive years, 9. the relation between the quantity of A. lineolatus Goeze and the age of alfalfa fields, 10. the appearance of this pest on other papilionaceous crops. As a result of these investigations it was found that A. lineolatus Goeze laid eggs, besides alfalfa, on different wild papilionaceous plants and weeds which grew on alfalfa fields and on their borders. Artemisia vulgaris L., Tanacetum vulgare L., Achillea millefolium L., Cichorium intybus L., Erigeron canadensis L., Melilotus albus Med., were the plants in which the pest laid numerous eggs mainly in September. In these plants the eggs were located in terminal parts, even 4 feet high above the level of the ground, while in alfalfa plants 0,1-3 inches. The beginning of eggs laying took place on alfalfa plants in late June and continued to early October. The females of spring brood laid aggs mainly in July - early August, the females of summer brood in september. The incubation period during the season of 1955 was 12-26 days and 20-32 days in 1956. The incubation period of wintering eggs was about 8 months. The average number of eggs produced per one female in 1954-1955 was 80 for spring brood and 34 for summer brood. It showed a considerable amount of variation for individuals. The larvae of spring brood begin to hatch in early May. The hatching continued to the second half of June. The larval development varied considerably in the different years. It was the shortest in 1956 (21 days) and the longest in 1955 (42 days). In laboratory conditions, the development was shorter. The larvae of summer brood appeared in July abd August. The period of their development was about 4 weeks. The adults appeared on the fields througout the season. The highest population of adults occured in late June - early July (spring brood) and in September (summer brood). The lifetime period was different for individual females. The average lifetime of spring brood females was 5 weeks and 3-4 of summer brood. The population of A. lineolatus Goeze was very numerous in many fields of alfalfa, causing great losses in seed production. It occured very numerous in alfalfa fields in different parts of Poland (Lover Silesia, south-east, and north regions of Poland). A positive correlation was found between the estimates of A. lineolatus Goeze population and the bud and flower fall. The quantities of A. lineolatus Goeze have been divided into three classes : 1. the low population (average 20 bugs per 100 sweeps) destroyed buds and flowers very little, 2. the higher population (average 120 bugs per 100 sweeps) caused injury to reproductive organs, distinct and easy to observe, 3. the highest population (average 250 bugs per 100 sweeps) destroyed all buds and caused total loss on alfalfa fields. A. lineolatus Goeze was unequally distributed on alfalfa fields. Especially, it appeared very distinctly on fields where this species was very numerous. According to the habitat conditions the quantities of A. lineolatus Goeze decreased or increased on the same fields in successive years. The same changes of quantities were observed on the different fields in the same year. This pest appeared more numerous in the older alfalfa fields. It appeared also on other papilionaceous plants. There it had not any economic importance. Periodically it was found on weeds on which it fed and laid eggs.
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