Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 63. (Budapest 1971)
Kovács, L.: Data to the knowledge of Hungarian Macrolepidoptera VI. Data with respect to migrating and spreading species
Now, if matters really stand so, the number of generations also looses its uncertainty aspect. In my opinion, the immigrating partial populations have, regardless of the area of development, a total of 3 generations. The first is the one which immigrates in two portions. Their second generation, shifted in time from each other, is indicated by the double summer peak. The third generation of the partial population, whose second brood is indicated by the first summer peak, appears at the turn of August —September, revealed by the continuosly high individual numbers, whereas the third brood of the partial population referred to by the second summer peak flies in October, in lower individual numbers owing to the less favourable weather conditions. The individual numbers of exigua rather fluctuate not only in the several seasons of the year but also from year to consecutive year in Hungary. The annual changes are well illustrable by the numerical data, established by the material of 40 light traps, of the period 1962—1967. The number of captured specimens was 111 in 1962, representing 40.5% of all exemplars caught until 1970. No more than 50 were caught in 1963, merely 15 in 1964, and only 3 in 1965. None was captured in 1966, and then 15 again in 1967. The strong fluctuation of the individual numbers and the complete absence of immigration in 1966 raise problems hardly answ r erable satisfactorily by the hitherto available data. One might suppose that the migrating specimens change their route, and also that their advance halts underway. A final reply can only be given when an organized international network will come into being. On the direction and further advance of the immigration, however, our home light trap network submits some information. For the sake of orientation, I have plotted also the years of observation along the localities of occurrence on the map, for the years 1962—1967 (Map 6). It can be established, first of all, that towards the north and the east the frequency of occurrences decreases together with individual numbers. Furthermore, the frequency of the years of occurrence is not evenly distributed, indeed, localities of multiannual observations group into foci, especially in the neighbourhood of the Balaton and the central part of the Great Plains. Between these, observations were rarely or not made at all; also, there extends a wide zone northwest of the Tisza without any observation of the species in the years under discussion. A consideration of the above statements implies that the immigration of exigua was of any greater extent only in three places during the examined years. It crossed the border along the line of the Mura and Dráva rivers in the Western Transdanubia, and advanced northwards in the western confines of the country and northeastwards in the Balaton region. The central group advanced in a wide zone along the two sides of the Danube towards the north-northwest. In the east, the migration crossed the border in the region of the Kőrös rivers and continued mainly northwestwards, more sparsely and at a slighter extent northeastwards. The migrations reached our borders again in the west locally and also in the north. According to the evidence of foreign literature, some examples arrive even in the neighbouring countries (HRUBY, 1964; STERZL, 1967). Evaluation of data S. exigua does not breed contiguously in Hungary, hence it belongs from this aspect to the migrating species. No part of the country forms an exception in this respect. Its immigration devolves in two, temporarily well discrete waves. The
