Effects of Larval Host Diameter on Body Size, Adult Density, and Parasitism of Cerambycid Beetles

435 Effects of larval host diameter on body size, adult density, and parasitism of cerambycid beetles

Peter F. Reagel, Michael T. Smith, Lawrence M. Hanks1

Abstract—In this study, we assessed the relationship between the size of bolts cut from pin oak trees, Quercus palustris Mu¨nchhausen (Fagaceae), and eastern white pines, Pinus strobus Linnaeus (Pinaceae), and the number and body size of cerambycid beetles (Coleoptera: Cerambycidae) that develop within them. From oak bolts emerged adult Graphisurus fasciatus (De Geer) (98% of beetles) and Xylotrechus colonus (Fabricius), while pine bolts produced Monochamus carolinensis (Olivier) (95%) and Astylopsis sexguttata (Say). The number of G. fasciatus was positively correlated with the diameter of the oak bolts, while the greatest number of M. carolinensis emerged from pine bolts of intermediate diameter. Body size of both species was positively correlated with bolt diameter. Rates of parasitism were very low, only 0.9% for oaks, and averaging 5.3 7 8.6% across pine bolts. Oak bolts yielded the braconid wasps (Hymenoptera: Braconidae) Wroughtonia ferruginea (Brues) and a species in the genus Atanycolus Fo¨rster (similar to Atanycolus charus (Riley)), and an ichneumonid (Hymenoptera: Ichneumonidae) in the genus Demopheles Fo¨rster. Pine bolts produced a braconid in the genus Digonogastra Viereck, and the tachinid ﬂy (Diptera: Tachinidae) Billaea monohammi (Townsend).

Re´sume´—Nous e´valuons dans notre e´tude la relation entre la taille des billes provenant de cheˆnes des marais, Quercus palustris Mu¨nchhausen (Fagaceae), et de pins blancs, Pinus strobus Linnaeus (Pinaceae), et le nombre et la taille corporelle des coleópte`res ce´rambycide´s (Coleoptera: Cerambycidae) qui s’y de´veloppent. Des billes de cheˆne, e´mergent des adultes de Graphisurus fasciatus (De Geer) (98% des coleópte`res) et Xylotrechus colonus (Fabricius), alors que les billes de pin libe`rent des Monochamus carolinensis (Olivier) (95%) et Astylopsis sexguttata (Say). Il y a une corre´lation positive entre le nombre de G. fasciatus et le diame`tre des billes de cheˆne, alors que le plus grand nombre des M. carolinensis e´merge des billes de pin de diame`tre interme´diaire. Il y a une corre´lation positive entre la taille corporelle des deux espe`ces et le diame`tre de la bille. Les taux de parasitisme sont tre`s faibles, seulement 0.9% chez les cheˆnes et en moyenne 5.3 7 8.6% dans l’ensemble des billes de pin. Les billes de cheˆne ont donne´ les bracons (Hymenoptera: Braconidae) Wroughtonia ferruginea (Brues) et une espe`ce du genre Atanycolus Fo¨rster (semblable a` Atanycolus charus (Riley)), ainsi qu’un ichneumon (Hymenoptera: Ichneumonidae) du genre Demopheles Fo¨rster. Les billes de pin ont geńe´re´ un bracon du genre Digonogastra Viereck et la mouche tachinide (Diptera: Tachinidae) Billaea monohammi (Townsend).

Larvae of most species of cerambycid beetles Here, we summarise research that assessed the feed subcortically in woody plants, and many relationship between the size of bolts cut from species are important pests in managed and trees and the number and size of cerambycid natural forests worldwide (Solomon 1995). For beetles that emerge, and parasitism rates. some cerambycid species, performance by the The study was conducted in a , 0.08 ha tree larvae is strongly inﬂuenced by the physical plantation (United States of America: Illinois: dimensions of larval hosts (Hanks et al. 2005), Champaign Co.; 40805006.4300N, 88812049.8800W) as well as parasitism rate (Hanks et al. 2001). with pin oaks, Quercus palustris Mu¨nchhausen

Received 7 March 2011. Accepted 7 July 2011. P.F. Reagel, L.M. Hanks,1 Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States of America M.T. Smith, USDA-ARS Beneﬁcial Insects Introduction Research Lab, Newark, Delaware 19713, United States of America Corresponding author (e-mail: [email protected]). doi:10.4039/tce.2012.39

Can. Entomol. 144: 435–438 (2012) ᭧ 2012 Entomological Society of Canada Downloaded from https://www.cambridge.org/core. University of Illinois at Urbana - Champaign Library, on 12 Dec 2017 at 14:50:57, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.4039/tce.2012.39 436 Can. Entomol. Vol. 144, 2012

Table 1. Total number (% female) and mean density (per m2 bark surface of bolt, 71 SD) of adult cerambycid beetles that emerged from bolts of pin oak and eastern white pine. Sex ratios of all species were not signiﬁcantly different from 1:1 (G-test for goodness of ﬁt, P . 0.05)

Subfamily Species Oaks Pines

Cerambycinae Xylotrechus colonus 13 (60%) 0 0.5 7 2.2 beetles/m2 Lamiinae Astylopsis sexguttata 0 21 (53%) 0.4 7 1.4 beetles/m2 Graphisurus fasciatus 647 (47.3%) 0 17.7 7 21 beetles/m2 Monochamus carolinensis 0 385 (52%) 17.9 7 19.5 beetles/m2

(Fagaceae), and eastern white pines, Pinus strobus G. fasciatus, suggesting that larvae of the two Linnaeus (Pinaceae) (oaks , 40 years old, species compete aggressively. Cerambycid larvae pines , 50 years old; average diameter of trunk can be opportunistic predators of other wood- [71 SD] at 1 m: 27 7 7and237 2 cm, respec- boring insects (e.g., Dodds et al. 2001). tively). During 6–19 July 2005, we felled six oaks Density of adult G. fasciatus (numberofbeetles and cut them into 81 bolts (63 from trunk, per unit bark area) was positively, though weakly, 18 from branches, mean diameter 0.17 7 0.08 m, correlated with bolt diameter (Fig. 1A; regres- 2 length 0.79 7 0.16 m). Bolt diameter was sion analysis, adjusted r 5 0.24; F1, 67 5 21.8; strongly autocorrelated with bark thickness P , 0.0001), suggesting that adult females pre- (adjusted r2 5 0.56, P , 0.0001). We felled three ferred to oviposit into larger bolts, and/or that pines and cut them into 72 bolts (42 from the survivorship of larvae was greater in such bolts. trunk, 30 from branches, diameter 0.12 7 0.07 m, Other studies of cerambycids also have reported length 0.8 7 0.17 m). We confirmed that few greater rates of oviposition and enhanced survi- adult insects emerged from the bolts during 2005 vorship in larger bolts (e.g., Hanks et al. 2005). by enclosing a subset (two oak, three pine bolts) Larger bolts may accommodate greater numbers in aluminium screen (2 mm mesh) in early fall. of larvae because they offer thicker phloem Neither adult beetles nor parasitoids emerged and cambial tissue for the larvae to feed (Hanks from those bolts until the following spring. In et al. 2005). Body size of G. fasciatus (length of April 2006, we enclosed the remaining bolts in right elytron) was positively, but weakly corre- screen, individually wrapping large bolts from lated with the diameter of their natal bolts (best trunk and larger branches (.0.1 m in diameter), fit regression equation: Y 5 0.002X 1 0.0077; 2 but wrapping smaller bolts (,0.08 m) together in adjusted r 5 0.012; F1, 506 5 7.13; P 5 0.0078). groups of 3–7 (n 5 3 and six groups of the smaller Of the 72 pine bolts, 44 (61%) yielded bolts for oaks and pines, respectively). Wrapped adult Monochamus carolinensis (Olivier) (95% bolts were checked for insects weekly through of beetles), and Astylopsis sexguttata (Say) September 2006. (Table 1). Of the latter species, 86% emerged We reared from the bolts 1066 cerambycid from three different groups of smaller branches, beetles of four species (Table 1). Of the 81 oak however, densities were not significantly bolts, 70 (86%) produced beetles, of which different between bolts cut from branches or 98% were Graphisurus fasciatus (De Geer) and from the trunk (means 7 SE: 1.88 7 1.1 and the remainder Xylotrechus colonus (Fabricius) 0.22 7 0.18 beetles/m2 of bark surface for branches (Table 1). Males and females did not differ in and larger bolts, respectively; Kruskal–Wallis emergence period (t-test of mean ordinal dates Q1,60 5 2.5, P 5 0.11). of emergence, t 5 0.13; df 5 442; P . 0.1). It is Densities of M. carolinensis were greatest in notable that 11 of the 13 adult X. colonus logs of intermediate size, although the correla- emerged from three oak bolts that produced no tion was weak (Fig. 1B; regression analysis,

᭧ 2012 Entomological Society of Canada Downloaded from https://www.cambridge.org/core. University of Illinois at Urbana - Champaign Library, on 12 Dec 2017 at 14:50:57, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.4039/tce.2012.39 Reagel et al. 437

Fig. 1. Relationship between the number of adult cerambycid beetles that emerged (per unit of bolt surface area) and bolt diameter for (A) bolts of pin oak (best fit regression equation Y 5 141X – 6.7) and (B) bolts of eastern white pine (relationship characterised by fitting equations to data and selecting that which maximised the coefficient of determination with all terms significant: Y 5 22 400X 3 – 13 360X 2 1 2330X – 93) (Quinn and Keough 2002; SPSS 2006).

2 adjusted r 5 0.21; F3,51 5 5.49; P , 0.0025). A Very few adult parasitoids emerged from oak similar parabolic relationship has been reported bolts, with an overall parasitism rate (i.e. number for a different Monochamus Dejean species of parasitoids/total number of insects) of 0.88%. (Zhang et al. 1993). Fewer beetles may have This ﬁnding was surprising, given the high emerged from the largest logs because their thick densities of beetle larvae in many bolts, and bark hindered oviposition, as has been reported for the fact that they had been exposed to the M. carolinensis in an earlier publication (Walsh parasitoid community for several months. From and Linit 1985). Consistent with G. fasciatus, oak bolts we reared the braconids (Hyme- body size of M. carolinensis was positively, but noptera: Braconidae) Atanycolus Fo¨rster species weakly correlated with diameter of pine bolts (a species similar to Atanycolus charus (Riley) (best ﬁt regression equation: Y 5 0.007X 1 0.014; (two females) and Wroughtonia ferruginea 2 adjusted r 5 0.09; F1,190 5 20.8; P , 0.0001). (Brues) (one of each sex), and an ichneumonid

(Hymenoptera: Ichneumonidae) in the genus References Demopheles Fo¨rster (two females). Voucher Allison, J.D., McIntosh, R.L., Bordon, J.H., and specimens were deposited in the Insect Collec- Humble, L.M. 2000. A new parasitoid (Diptera: tion of the Illinois Natural History Survey, Tachinidae) of Acanthocinus princeps (Coleoptera: Champaign, Illinois, United States of America. Cerambycidae) in North America. Journal of the Parasitism rate for beetles that emerged from Entomological Society of British Columbia, 97: 3–5. 7 Bashford, R. 1994. Life history and mortality of the pine bolts averaged 5.3 8.6%, including a longicorn Epithora dorsalis Macleay (Coleoptera: braconid in the genus Digonogastra Viereck Cerambycidae) in Tasmania. Australian Entomologist, (one female), and the tachinid fly (Diptera: 21: 125–136. Tachinidae) Billaea monohammi (Townsend) Dodds, K.J., Graber, C., and Stephen, F.M. 2001. (28 adults, approximately equal numbers of Facultative intraguild predation by larval Cerambycidae (Coleoptera) on bark beetle larvae (Coleoptera: females and males). Billaea Robineau-Desvoidy Scolytidae). Environmental Entomology, 30: 17–22. species are known to parasitise larvae of a dif- Hanks, L.M., Paine, T.D., and Millar, J.G. 2005. ferent Monochamus species (Allison et al. 2000). Influence of the larval environment on performance Wood-boring insects can be shielded from and adult body size of the wood-boring beetle parasitoids by the woody tissues of their hosts Phoracantha semipunctata. Entomologia Experi- mentalis et Applicata, 114: 25–34. (e.g., Hanks et al. 2001). In our study, however, Hanks, L.M., Millar, J.G., Paine, T.D., Wang, Q., and the parasitism rate of M. carolinensis was not Paine, E.O. 2001. Patterns of host utilization by correlated with the diameter of pine bolts two parasitoids (Hymenoptera: Braconidae) of (regression P . 0.05). Very low rates of para- the eucalyptus longhorned borer (Coleoptera: sitism also have been reported for other species Cerambycidae). Biological Control, 21: 152–159. Quinn, G.P. and Keough, M.J. 2002. Experimental of cerambycid beetles (e.g., Bashford 1994). design and data analysis for biologists. Cambridge University Press, Cambridge, United Kingdom. Solomon, J.D. 1995. Guide to insect borers of North Acknowledgements American broadleaf trees and shrubs. United States Department of Agriculture Forest Service Agriculture We thank E.E. Graham, R.F. Mitchell, A.M. Handbook, 706: 1–735. Ray, M.L. Richardson, D.E. Philpott, M.C. SPSS. 2006. SigmaPlot 10 user’s guide. SPSS Inc., Currier, and J.F. Hitchens for assistance in the Chicago, Illinois. Walsh, K.D. and Linit, M.J. 1985. Oviposition biology field, and J.J. Rodriquez, A.A. Velario, J.B. of the pine sawyer Monochamus carolinensis Whitfield, and N.E. Woodley for help with tax- (Coleoptera: Cerambycidae). Annals of the onomy. We appreciate funding support from the Entomological Society of America, 78: 81–85. Agricultural Research Service of USDA under Zhang, Q.H., Byers, J.A., and Zhang, X.D. 1993. agreement #58-1926-3-339, and the Alphawood Influence of bark thickness, trunk diameter and height on reproduction of the longhorned beetle, Foundation. This research was in partial fulfil- Monochamus sutor (Col., Cerambycidae) in burned ment of a Ph.D. degree for P.F.R. from the larch and pine. Journal of Applied Entomology, University of Illinois at Urbana-Champaign. 115: 145–154.