Enumerative sampling plans for grasshopper egg pods in northern Benin

The spatial distributions of egg pods of two grasshopper species, Hieroglyphus daganensis Krauss and Cataloipus fuscocoeruleipes Sjostedt, collected from three oviposition sites, Piliostigma thonningi (Schumach.) Milne-Redhead, Vetiveria nigritana (L.) and Sorghum bicolor (L.) Moench, are described using Taylor's power law. Both grasshopper species showed a highly aggregated distribution with Taylor's index of dispersion ranging between 1.380 and 1.709, except for C. fuscocoeruleipes from S. bicolor where an index of dispersion of 0.885 indicated a regular distribution. Enumerative sampling plans incorporating Taylor's power law are presented to estimate mean grasshopper egg pod densities with predefined levels of reliability for future studies. For egg pod densities of < 1.0 m(-2), optimal sample sizes at a site consist of 50 P. thonningi shrubs, 125 V nigritana clumps and 150 S bicolor patches with a reliability level of D = 0.3. This would demand a team of seven people to work for approximately 15 h.