When effects of pesticides are tested on nontarget invertebrates, substrate exposure is mostly used. Routes of uptake of pesticides by saprotrophic invertebrates may, however, also occur through the food, since the litter layer will be their main food source. These organisms live in close contact with the soil surface and litter layer. The ecotoxicity of the pesticides benomyl, carbofuran, and diazinon was investigated in a series of experiments. The toxicity was tested in lethal concentrations (leading to LC50 estimations), and sublethal concentrations leading to no‐observed‐effect concentration (NOEC) estimations on growth. Both substrate and dietary exposure were used to evaluate the most critical exposure route for each case. For food exposure, the chemicals were offered in ground leaves, while for substrate exposure the test organisms were kept on treated sand. Experiments were done with the tropical isopod Porcellionides pruinosus. For all three pesticides, substrate exposure was more critical than dietary exposure. The LC50 values (active ingredient per dry mass of food or soil) for benomyl, carbofuran, and diazinon, when mixed with food, were >31,000, 485, and 74.15 μg/g, respectively, and when mixed with sand 1,221, 21.41, and 3.03 μg/g, respectively. Sublethal effects on body growth were found for benomyl (NOEC = 1,000 μg/g) and diazinon (NOEC = <8.71 μg/g) after dietary exposure, but no effects were found in the course of the experiment for substrate exposure. Based on the results, it is concluded that the exposure route is of great importance for determining lethal effects as well as sublethal effects of pesticides on nontarget invertebrates in soil. The most critical exposure route depends both on the mode of action of the chemical and on the toxicological end point considered.

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The populations of two dominant isopod species in a Pinus merkusii forest on the southern slope of mount Ungaran in central Java, Indonesia, were periodically sampled during one year using Tullgren extractions from soil cores. The aim of the research was to collect more information about the life-cycles of tropical isopods by analysing size-class distributions of two sympatric isopod species, belonging to the genus Burmoniscus. Biomass of the populations was estimated from length-weight conversions established for each species in the laboratory. The efficiency of the Tullgren extraction method was estimated by comparison to hand sorting; no difference was found between these methods.The abundance of the two species differed significantly with time. Burmoniscus Sp. A was more abundant during the wet season, whereas the population fluctuations of Burmoniscus Sp. B were more spread over the year. Reproduction of both species took place in the wet season. Burmoniscus Sp. A had one generation per year, while for Burmoniscus Sp. B the situation was unclear due to extensive overlap of size classes. Comparisons were made with isopod abundance in other tropical and temperate forests. The mean density of the two species found in this study was 258 m-2 for Burmoniscus Sp. A and 272 m-2 for Burmoniscus Sp. B, while biomass was 80.4 mg m-2 and 37.6 mg m-2, respectively. The data suggest that densities of isopods in tropical pine forests may be considerably higher than in comparable temperate ecosystems.