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An Analysis of Malaise-Trap Effectiveness in Assessing Robber Fly (Diptera: Asilidae) Species Richness

McCravy, Kenneth W.
Northeastern naturalist 2017 v.24 no.1 pp. 15-24
Asilidae, Malaise traps, deciduous forests, habitats, insects, inventories, sampling, species diversity, tallgrass prairies, Illinois
Little quantitative information is available on the effectiveness of Malaise traps in estimating insect species richness. I used the Chao1 nonparametric species richness estimator to evaluate the effectiveness of Malaise traps in assessing species richness of robber flies in west-central Illinois burned and unburned deciduous forest and tallgrass prairie habitats. Two of 12 traps yielded asymptotic species richness values, with remaining traps requiring fold increases ranging from 3.1 to 20.9 to reach asymptotic richness. Overall, observed species richness was over 85% of estimated species richness, but a 3.9-fold sample-size increase would have been required to reach asymptotic species richness. For individual habitats, estimated fold increases in sample size ranging from 1.9 to 9.7 would have been needed to reach asymptotic species richness. These results show that Malaise traps are effective in sampling robber flies, but asymptotic species richness would be difficult to achieve. Lower target coverage levels may be practical in terms of sampling effort and cost, and use of complementary sampling methods could improve the completeness of inventories.