Mark Alderweireldt

Habitat manipulations increasing spider densities in agroecosystems: possibilities for biological control?

Field experiments with habitat manipulations were conducted in Belgian crop fields in order to follow changes in abundances and species composition of the spider taxocoenosis. Spider densities increased spectacularly in plots with holes (up to 13 times) in the soil. Moreover, this density increase depends on the diameter of the holes, with diameter 9.5 and 5 cm being the most effective. Species composition in the plots with holes also changed considerably compared to control plots. Exclusively web building Linyphiidae (Bathyphantes gracilis and Lepthyphantes tenuis) took far more advantage of the new possibilities offered by the habitat for web construction than non web‐building spiders. B. gracilis preferred holes with a diameter of 5 cm whereas L. tenuis was more abundant in the D9.5 cm plots. It is concluded that this kind of relatively simple habitat manipulations are advantageous for population levels of certain beneficial polyphagous predators, such as spiders. This might offer possibilities for biological control of pest populations.

A review of the nebulosa-group of Pardosa Koch 1847 in Africa, a complex with some highly variable species (Araneae Lycosidae)

The African representatives of the Pardosa nebulosa-group are revised. This group now includes 10 species, five of which are new: P. alticola, P. kavango, P. nostrorum, P. paleata and P. thompsoni. The other five are P. gefsana Roewer 1959, P. injucunda (O.P.-Cambridge 1876), P. lusingana Roewer 1959, P. messingerae (Strand 1916), P. naevia (L. Koch 1875). P. lycosina Purcell 1903, only known from females, is a possible additional species. All the species are described and much attention is paid to intraspecific variability. In P. injucunda the high variability is thought to reflect the existence of different biospecies. An illustrated key to the males is provided. The generic placement of the group and the taxonomic level of the taxa it contains, are discussed.

A revision of the African representatives of the wolf spider genus Evippa Simon, 1882 (Araneae, Lycosidae) with notes on allied species and genera

The African representatives of the wolf spider genus Evippa are revised. Eight species are included, of which one is known from males only and two from the female sex. Evippa aequalis, Evippa projecta, Evippa russellsmithi and Evippa jocquei are described as new. Some allied species are redescribed and notes on nomina dubia, misplaced species and new synonymies are provided.

Belgian carabidological research on high-input agricultural fields and pastures: a review

In this review a compilation is given on the state of knowledge of the ecology and dynamics of carabid beetles occurring on high-input agricultural fields and pastures in Belgium. In our country, such carabidological studies have mainly concentrated on widely distributed crops such as different cereals (e.g. winter wheat) and maize. This last crop only received attention during the last decade because of its ever increasing importance and impact in the agricultural landscape. Studies on the carabid fauna in Belgian crop fields and pastures have concentrated on many different ecological and biological aspects: sampling methodology, species composition and diversity, larval morphology, habitat and microhabitat preferences, phenology and life cycle reconstruction, absolute abundance and population dynamics, diel activity patterns, feeding ecology in relation to their importance as polyphagous predators of insect pests, the influence of management practices, etc...

An introductory study of house spiders (Araneae) in Belgium

Summary More than 800 spiders were collected in 43 houses heated in winter, distributed mainly in the northern part of Belgium. Information required for the collections to be eligible for the project was: address, construction year, type of house, and surroundings. The spiders were qualified as ‘house spiders’ or ‘garden spiders’. Of the 93 species collected, 19 could be defined as house spiders. Pholcus phalangioides was the most common, followed by Eratigena atrica and Steatoda triangulosa. Garden spiders enter the house much more often in houses in a rural environment than in those situated in clusters, and mainly in spring. The spiders are most common in autumn when many of them are breeding. The common house spiders colonize houses shortly after their construction.