Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 91. (Budapest 1999)

Skuhravá, M. ; Skuhravý, V.: Gall midges (Diptera: Cecidomyidae) of Hungary

sioptera eryngii living in stem galls on Eryngium campestre, E. maritimum and E. amethysthinum. The following three species have an interesting and remarkable occurrence. Oligotrophus szepligetii larva causing pustule galls on the leaves of Acer tataricum seems to have a centre of its occurrence in the Pannonian lowlands in Hungary. Limits of its distribution area run in the southern part of Slovakia along the distribution area of its host plant. This species may be designated as a typical Pannonian species. As far as it is known, there is no evidence about its occurrence towards east to the Black Sea, where the distribution area of its host plant is spread (Fig. 3). Kochiomyia kochiae causing galls on Kochia prostrata seems to be the only one representative of the Pontic-Pannonian elements. It was found only at a few localities along the coast of the Black Sea and at several localities in Hungary (Fig. 2). Zeuxidiplosis giardi larva causing galls on Hypericum perforatum is noted for its disjuncted area of distribution although its host plant is regularly spread over the western part of the Palaearctic Region and it is the second gall midge species associated with this host plant occupying nearly the whole area of its host plant species. Long-term changes in population dynamics Gall midges are permanent but changing components of ecosystems in nature. Species composition changes in the course of each year and also the population density increase or decrease during one or several years. It is possible to observe such changes in population dynamics when comparable data are available. Data of Hungarian researchers give evidence that several gall midge species which were observed at the beginning of the 20

th century either quite disappeared by now, or are at present very rare. Dasineura hypericin D. tympani, Macrolabis heraciei, Placochela ligustri and P. nigripes show increasing population density. They were rare in the first half of the 20

th century but, at present, they are abundant. Increasing population density of gall midges associated with cultural plants may remain quite hidden for a long time and it is not usually observed even by researchers of plant protection. It may change abruptly into outbreak and such species become pests, as it happened, for example, with Haplodiplosis marginata. Dasineura irregularis, D. marginemtorquens and Rabdophaga rosaria display decreasing population density. They occurred abundantly in the past but at present they occur only scarcely. The majority of gall midges belongs to species with stable (constant) population density. The population density of those species at present seems to be approximately on the same level as it was in the past, for example may be given Dasineura medicaginis, D. plicatrix, D. urticae and Oligotrophus szepligetii. Galls of Oligotrophus szepligetii on young shrubs and trees of Acer tataricum are relatively abundant each year. They were observed by researchers in Hungary many times, past and present. It seems that the population density of O. szepligetii fluctuates but remains on a relatively high level all the time. Several gall midge species which occurred relatively abundantly in the past quite disappeared from the country and some of them may be consider to be extinct in the terri -