Spiders are arthropods belonging to the order Araneae of the class Arachnida. More than 40,000 species of this order have been described so far, a number that is constantly growing. These arthropods are naturally present on all continents, except Antarctica, and occupy different terrestrial environments, with greater variety in tropical regions.
Spiders, mostly nocturnal, are found in diverse ecological conditions. In addition, they present distinctions in their morphological characteristics and have different predation strategies and dispersal modes.
Agroecology has precepts that seek to develop agricultural production systems with greater sustainability and, for that, management practices that enhance natural biological control are necessary. In this context, spiders, like other arachnids, are predators and feed mainly on insects and, as a result, are identified as natural enemies and can efficiently control insect pest populations. Spiders in the Lycosidae, for example, can kill more than 50 times the amount of crickets they are able to feed on. Other studies have shown that the increased activity of spiders in certain agroecosystems contributes to the reduction of leafhoppers.
Under normal conditions, some spiders can travel about 20 meters per night, on the ground or in the vegetation. In adverse conditions, they can move 100 to 200 meters per night in search of food and better environmental conditions, thus, they are able to prey on insects over a large area and disperse easily. There are species that capture by stalking and ambus, and others that use webs in different shapes to trap their prey.
Spiders of different species may be necessary for biological control, however, the same spiders are not efficient in all agroecosystems nor against all types of prey, as they differ in hunting strategies, habitat preference and activity period. In addition, some measures are important for the preservation of predation within an agroecosystem, such as the reduction of chemical and physical substances within the habitats and the adoption of natural refuges for these predators.
Thus, it is possible to understand the importance of spiders for the biological control of pests in agroecological systems, and their diversity is an indicator of stability, productivity and complexity of the system. More studies on the predation of spiders on insects are essential, as they allow the improvement of conservationist management, reducing damage to the environment and producing knowledge about local biodiversity.
REFERENCES
ANDRADE, Etielle Barroso de et al. Aranhas (Arachnida; Araneae) em horta agroecológica no município de Parnaíba, Piauí, Brasil, e considerações sobre o seu papel como inimigos naturais e indicadores da qualidade ambiental. Embrapa Meio-Norte-Circular Técnica (INFOTECA-E), 2007.
AQUINO, Adriana Maria de; CORREIA, Maria Elizabeth Fernandes; AGUIAR-MENEZES, Elen de Lima. Aranhas em agroecossistemas. Seropédica- RJ: Embrapa Agrobiologia-Documentos (INFOTECA-E), 2007.
CIVIDANESS, Francisco Jorge et al. Diversidade e distribuição espacial de artrópodes associados ao solo em agroecossistemas. Bragantia, v. 68, n. 4, p. 991-1002, 2009.
CUNHA, José Alex da Silva et al. Atributos agroecológicos de solo e caracterização de predadores generalistas no cultivo de melancia nos tabuleiros litorâneos do Piauí, Brasil. Revista Brasileira de Agroecologia, v. 9, n. 1, p. 269-281, 2014.
GONZAGA, Marcelo O. et al. Ecologia e comportamento de aranhas. In: VASCONCELOS, Heraldo L. Ecologia e Conservação dos cerrados, campos e florestas do Triângulo Mineiro e Sudeste de Goiás. Rio de Janeiro: Editora Interciência, 2020. P. 221-241.
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