Partial Life Tables From Three Generations of <I>Enaphalodes rufulus</I> (Coleoptera: Cerambycidae)

Abstract

We used life table analyses to investigate age specific mortality and to better understand the population dynamics of the red oak borer, Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae). We continually sampled populations within 177 trees at primarily two sites in the Ozark National Forest in Arkansas throughout three (2-yr) generations. The first cohort (adults emerged in 2003) was sampled during a severe population outbreak, whereas the second and third (2005 and 2007) were sampled during the population crash that followed. Generation mortality was 94% in 2003 and 99% in both 2005 and 2007. Estimates of apparent mortality indicated that the E. rufulus population crash likely occurred during or before the first overwintering period (2003-2004) of the generation that emerged as adults in 2005. We found limited evidence for density dependent mortality, which suggest that intraspecific competition after the first active feeding period was apparently not an important mortality factor during E. rufulus development. Life tables revealed that E. rufulus larvae generally experienced the greatest apparent mortality during the second summer of active feeding (80-94%) when larvae were feeding in, and moving between phloem and sapwood. The least apparent mortality was incurred during the following spring and early summer (26-67%) when late stage larvae and pupae were deepest and most protected within sapwood or heartwood tunnels. We found very little evidence for mortality from associated species. Scarring of vascular tissue in response to E. rufulus feeding occurred during early life stages and may be an important tree resistance mechanism and E. rufulus mortality factor.

Do Native Insects and Associated Fungi Limit Non-Native Woodwasp, Sirex noctilio, Survival in a Newly Invaded Environment?

“…High levels of early-stage mortality indicate that initial conditions in pines were very important for Sirex survival. This same trend was reported from life tables of other wood-inhabiting insects [ 49 – 52 ]. It follows that mechanisms of tree resistance would be most effective at the early stages of insect attack: female oviposition or larval establishment.…”

“…Indeed, tree resistance appears to be the most important factor limiting populations of many bark- and wood-boring insects (e.g. [ 52 – 56 ]).…”

Life history and bionomics ofGlycobius speciosus(Coleoptera: Cerambycidae: Cerambycinae: Clytini)

“…Hay reported both 33% (1972) and 40% (1974) early instar mortality of E. rufulus occurring while larvae were feeding in the phloem immediately under the bark. A much lower percentage occurred in a study by Petit et al (1988) on the predation of later instars when they were 3–7 cm under the bark and Haavik et al (2012) observed a single probable attack in 3 generations. The success of bird predation also relies quite heavily on accessibility.…”

“…Between late summer of the first year and the following spring, during which time SMB larvae extended their galleries to about 30 cm and overwintered for the first time, 27% died. Sources of mortality for other tree-inhabiting cerambycids over a comparable period in their life history include intraspecific competition (Hanks et al 2005— P. semipunctata ), production of scar tissue by the tree (Haavik et al 2012— E. rufulus ), interspecific competition, fermenting medium or wound sap and the nitidulids it attracted, and woodpecker predation (Hay 1974— E. rufulus ). Only woodpecker predation was substantiated in this study.…”

Spatial patterns of within-treeEnaphalodes rufulus(Coleoptera: Cerambycidae) attacks during outbreak conditions in the Ozark National Forest in Arkansas, United States of America

“…Enaphalodes rufulus larvae were shown to be facultative intraguild predators in a laboratory setting (Ware and Stephen 2006). If facultative predation also occurred in field scenarios, that behaviour may account for some proportion of E. rufulus larval mortality attributed to unknown causes (Haavik et al 2012a). These interactions may affect both how female E. rufulus choose to distribute oviposition on selected hosts and the survival of E. rufulus larvae.…”