The paper surveys overlap between corpus linguistics and variationist sociolinguistics. Corpus linguistics is customarily defined as a methodology that bases claims about language on usage patterns in collections of naturalistic, authentic speech or text. Because this is what is typically done in variationist sociolinguistics work, I argue that variationist sociolinguists are by definition corpus linguists, though of course the reverse is not true: the variationist method entails more than merely analyzing usage data, and not all corpus analysts are interested in variation. But that being said, a considerable and arguably increasing number of corpus linguists not formally trained in variationist sociolinguistics are explicitly concerned with variation and engage in what I call corpus-based variationist linguistics (CVL). I first discuss what unites or divides work in CVL and in variationist sociolinguistics. In a plea to cross subdisciplinary boundaries, I subsequently identify three research areas where variationist sociolinguists may draw inspiration from work in CVL: conducting multi-variable research, paying more attention to probabilistic grammars, and taking more seriously the register-sensitivity of variation patterns.

Patterns of parasite infestation by plerocercoid forms of the tapeworm Ligula intestinalis (Cestoda, Pseudophyllidea) in the second intermediate host, the roach Rutilus rutilus, were analysed in three fish populations of South-Western France during 1998. In all three studied sites, i.e. Pareloup Lake, Lavernose-Lacasse and Muret gravel pits, roach were commonly parasitized with plerocercoids. A strong increase in prevalence, mean number of parasites and parasitic load was observed in the youngest hosts with a maximum peak reached in the medium-age (2+, 3+)roach classes. Such trends as a function of host fish age would indicate the occurrence of parasite-induced host mortality, with the most heavily infected fish specimens being removed from the three roach populations. The three roach populations infected by L. intestinalis exhibit different patterns of parasite-induced mortality which could correspond to different possible ecological and evolutionary responses associated with local variation in host-parasite interactions. The parasite-induced host mortality observed, i.e. direct mortality caused by pathogenic effects and /or enhanced fish predation by piscivorous birds to increase parasitic transmission is discussed within the context of the adaptative parasite-induced manipulation hypothesis.

Schooling fish may aggregate in very high densities covering very small areas. Thus the probabilityof hitting such high-density spots during a large-scale sampling is very low. The sampling fluctuations of the tail of the histogram are thought to be very significant. The stock biomass estimate and its precision rely greatly on how precisely the tail of the histogram can be sampled. In order to acquire elements for improving survey designs and abundance estimators wc study here the relation in space that the high values have with the other values. A disjunctive kriging approach is used. Different quantiles of the histogram are coded by indicators. The spatial structure of each indicator and its spatial covariation with the others are studied by computing experimental indicator variograms and cross-variograms. Such analysis is applied to dissect finely the spatial structure of a Norwegian herring stock sampled acoustically. It is shown that when going from low-density areas to high-density ones, intermediate values are not necessarily crossed. Thus a particular disjunctive kriging model with no transition in space is well adapted to the herring data. The model is based on the regressions of each indicator on the one immediately below it. In the model one can estimate the probability for the fish density to trespass a given cut-off at a given location when knowing that the density trespasses lower cut-offs at surrounding points. It is shown on the data that the high densities are structured and show small aggregations. Then it is shown that having trespassed a certain cut-off, i.e. inside the corresponding areas in space, the high-density aggregations can be considered to be positioned independently from the other values. These areas, where the structuring of the high values is not correlated to the structuring of the other values, are mapped using the fitted disjunctive kriging model. The implications for survey designing of the existence of such areas and of their geometry are discussed. Also discussed is the possibility of stratifying the data in spatially uncorrelated boxes when deriving the biomass estimate and its precision, on the basis of an observed spatial non-correlation property between the spatial distribution of different quantiles.

The human body louse aggregates on filter paper impregnated with an aqueous extract of louse faeces. Chemical analysis of the faeces revealed the presence of haemoglobin, xanthine, hypoxanthine, uric acid and ammonium salts. Of all these compounds, only ammonium salts caused marked aggregation of lice. Excretory products of other insects and ticks also failed to induce aggregation. Total faecal material was more attractive than ammonium, and led to greater aggregation of females than of males. Antennectomized lice reacted neither to faeces extract nor to ammonium carbonate solution.