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Summary1. Wood decomposition is driven primarily by microbial activity but proceeds at greatly varying rates depending on regional or local differences in physical conditions and other determinants. Although many arthropod taxa (e.g. termites, wood-boring beetles) are known to consume or excavate dead wood, their contributions to the decay process remain largely unmeasured. 2. Quantifying arthropod contributions to wood decay is fraught with challenges, but no guidelines are available to assist researchers in designing and carrying out studies of this kind. We therefore sought to provide a critical review of previous studies on this important topic and discuss methodological considerations that may benefit future researchers. 3. The biggest challenge inherent to such research involves excluding arthropods from dead wood (i.e. the reference treatment) without otherwise affecting the decay process. Because mesh bags are likely to alter physical conditions relative to unenclosed substrates and insecticides are likely to inhibit microbial growth, additional experimentation is needed to isolate the arthropod effect. Alternatively, partial exclusion or temporary exposure methods may produce less confounded results. 4. In determining the initial volume of a wood sample (e.g. to estimate the initial mass using specific gravity data), there is a trade-off between the accuracy of this measurement and the realism of the study. A method involving image analysis is described for obtaining accurate initial volume estimates for naturally occurring woody substrates. When measuring changes in specific gravity during the decay process, initial sample volumes must be used in these calculations as opposed to the water displacement technique which fails to measure wood removed by arthropod activity. 5. Termites carry large amounts of soil into dead wood, and this behaviour complicates efforts to measure their contributions to wood decay. A novel method for isolating termite soil by burning the wood is described, and some preliminary results are presented. 6. These and other recommendations described herein should aid efforts to quantify the contributions of arthropods to wood decay. Such research is of great interest given the broad importance of dead wood to forest ecosystems-including its role in carbon storage-and the diversity and conservation concern of the species involved.

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Abstract. Experimental efforts to determine how insects influence terrestrial wood decomposition are few, especially in temperate regions. To address this need, a five-year exclusion study was conducted in northern Mississippi, U.S.A., to quantify insect contributions to wood decay using one-meter loblolly pine (Pinus taeda L.) bolts. The study included three treatments: (1) ''partially protected'' bolts that were placed on cypermethrin-treated soil to exclude subterranean termites (Isoptera: Rhinotermitidae: Reticulitermes spp.) while permitting colonization by beetles (Coleoptera) and other saproxylic taxa, (2) ''fully protected'' bolts that were placed on cypermethrin-treated soil and enclosed within screen cages to protect against all insects and (3) ''unprotected'' bolts that were not subjected to either exclusion treatment. The full insect community consumed approximately 15-20% of wood volume in unprotected bolts, about six times more than in partially protected bolts from which termites were excluded. There were no differences in specific gravity (based on initial wood volume) or mass loss among treatments, however. It is not clear whether these findings are due to an inhibition of microbial decomposers by insects (e.g., antimicrobial compounds secreted by termites or ants), a stimulatory effect of the exclusion treatments (e.g., cypermethrin stimulating fungal growth or cages favorably altering wood moisture), or some combination of both. When based on final water-displaced volume, specific gravity was significantly higher for unprotected bolts than for those fully protected, probably because termites selectively consume the least dense wood. By the end of the study, about 20% of the final dry weight of unprotected bolts consisted of termite-imported soil. Wood volume consumed and soil content decreased with distance from the ends of the bolts whereas water content exhibited the opposite pattern. We detected a significant negative relationship between water content and volume consumed by termites, possibly because water content decreases with increasing wood density and termites tend to avoid high density wood. While insects clearly consume large volumes of wood in southeastern U.S. forests, our results suggest they do not act to accelerate mass loss beyond what is achieved by microbial decomposers. More research is needed to confirm this, however-especially given the uncertainties inherent to exclusion studies.

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The impact of foraging by Monock;tmus titillator (FAB.) on within-tree populations of Dendroctonusfrontalis ZIMM. was described. Total population estimates for D.frontalis and inner bark area foraged by M. titillator were computed for 89 loblolly pine, Pinus taeda L., sampled over a 3 year period. Frequency histograms were prepared for the surface area of habitat infested, area foraged by M. titillator, and within-tree populations of D. frontalis. These data were used to calculate the proportion of area foraged by M. titillator, the proportional D. frontalis mortality for the entire tree, and the proportional mortality occurring in the foraged area.Histograms showing the variation of these components were prepared and described using nonlinear mathematical models. Ca. 20 ~ of the infested surface area was foraged by M. titillator. Mortality to D. frontalis on a per tree basis was ca. 14 ~. Mortality in the area foraged by M. titillator was ca. 70 ~. These estimates were highly variable between individual trees and a procedure for predicting the probability of a given level of foraging and mortality was described. Sources of variation influencing foraging by M. titillator and mortality to D. frontalis were investigated. Variation between years and season followed similar trends with both foraging and mortality increasing from the base to the top of the infested bole. Variation between tree size-class was highly significant. Larger size-class trees had substantially greater foraging and mortality than did the smaller size-classes. Mortality within the foraged area was also found to be greater at the extremes of the infested bole.The southern pine sawyer, Monochamus titillator (FAB.) (Col. : Cerambycidae) is a member of the complex arthropod community that results from colonization of pine trees, Pinus spp., by the southern pine beetle, Dendroctonus frontalis ZIMM. (Col. : Scolytidae). In association with D. frontalis, M. titillator has been identified to be an interspecific competitor for food resources and habitat (COULSOY et al., 1976(COULSOY et al., & 1979. Competition occurs as a result of spatial and temporal coincidence in development of both species in the inner bark of the host. Foraging by M. titiltator results in mortality to D. frontalis.(1) Texas Agricultural Experiment Station No. TA15244.