Arthropods in epiphytes: a diversity component that is not effectively sampled by canopy fogging

Insecticide fogging is often used to document arthropod species richnessin forest canopies, but this technique may not effectively sample invertebratesthat are concealed within a variety of microhabitats. We quantified the effectsof fogging on invertebrates in canopy epiphyte mats of a Costa Rican cloudforest by extracting arthropods from 18 paired pre- and post-fogging samples.Mean abundance and morphospecies richness of living arthropods were respectivelyreduced by 33 and 30% in epiphyte material after fogging, but most organismssurvived the treatment. Relative abundances of major taxa were unaffected byfogging. Herbivores were less abundant after fogging than other trophic groups,and the median body length of non-mite arthropods present in epiphytes wassignificantly smaller after fogging. Examination of seven post-fogging samplesshowed that many arthropods killed by insecticide remained trapped within theepiphyte material. These results provide the first quantitative assessment of aspecific component of arboreal arthropod biodiversity that is missed by thefogging technique.