The road of an insect group from systematic control to the Red Data Book

Abstract

The publication describes the contradiction that Orthoptera can be the cause of nutrition problems, targets of systematic control, the intensively researched objects of zoo-ecology and, through their sensitive species, the flagships of Hungarian and international nature conservation at the same time. This contradiction is visible in Hungary mainly in the course of history (e.g. Locusta migratoria, which formerly caused huge destruction, is now a protected species, included in the Red Data Book). On a global scale, however, four out of the 25 hot spots of continental biodiversity of the Earth are regularly affected by plagues caused by locusts. 200 ecoregions of Global worthy of outstanding attention concerning conservation biology (of which 136 are continental), 12 are also affected by plagues caused by locusts.
In the frame of a global overview we will survey the most important characteristic features and differences between the biology and habitat choice of the two species (Schistocerca gregaria, Locusta migratoria) causing the most significant destruction worldwide. Among the numerous differences a basically determining factor of the spreading of these locusts seems to be that while Schistocerca gregaria can be considered a strongly polyphagous insect with dipetalous preferences, Locusta migratoria is a specialist, i.e. oligophagous nutrition and mainly eats grasses. The weather needs of the two species also significantly differ. While heavy rain forces the Locusta migratoria populations to local migration, it causes severe mortality among the Schistocerca gregaria individuals.
In the Carpathian Basin Locusta migratoria used to be the main character of plagues of locusts until 1889-1890, however, from then on Dociostaurus maroccanus became dominant due to the landscape and habitat transformations especially characterised by the total drainage of marshy habitats. The chronology of historical data raises the possibility of a southern-northern invasion too; however, several facts seem to contradict this. Based on the data at our disposal Lósy (1904) and Adamovic s (1959) opinion - according to which Dociostaurus maroccanus is a late discovered Orthoptera species characteristic in Hungary of the alkaline soil of the Great Plains, which attained more extensive habitats owing to the drainages, agricultural cultivation and desistance from agricultural cultivation - seems to be more grounded. In the nutrition of Dociostaurus maroccanus grasses are dominant, consequently, apart from pastures, it caused damage mainly in barley and other similar cultivated cultures. By now this species has lost its former economic significance in most European countries, but elsewhere (North-African and Central-Asian countries) it still regularly occurs in significant numbers and has preserved its status as a “pestiferous” animal. This naturally also applies to the Locusta migratoria and Schistocerca gregaria species mentioned above.
In the 21st century it is impermissible from nature conservation, human-hygienic and rational aspects that the management of “catastrophes” resulting from the increase in the number of Orhtoptera in the above-mentioned areas occurs in an ad hoc way, with drastic interventions. Within the frame of control strategies more and more attention is paid to forecasting and planning preventive interventions in the early phases of gradations. Naturally, solving problems affecting several countries requires international co-operation and the co-operation of organisations working for different purposes and governments by considering the possibilities and limitations of political and economic relations. The implementation of such co-operation is further aggravated by the fact that it is mostly necessary in the underdeveloped areas of the Third World.