Xyleborus affinis Eichhoff colonized wind thrown timber in the moist floodplain habitats of Central Michigan. Single adult females constructed a complex gallery system consisting of phloem–sapwood interface tunnels and sapwood tunnels. An average of 24 progeny adults and a sex ratio of 14 females to 1 male were found in mature galleries after the first of September

Bowker, Richard G

Bunce, Mark A

Harlan, John E

Roeper, Richard A.

English

Valparaiso University

The Great Lakes Entomologist Volume 48 Numbers 3/4 -- Fall/Winter 2015 Numbers 3/4 -- Fall/Winter 2015 Article 2 October 2015 Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central Michigan Richard A. Roeper Alma College, rroeper@yahoo.com Mark A. Bunce Alma College John E. Harlan Alma College Richard G. Bowker Alma College Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Roeper, Richard A.; Bunce, Mark A.; Harlan, John E.; and Bowker, Richard G. 2015. "Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central Michigan," The Great Lakes Entomologist, vol 48 (3) Available at: https://scholar.valpo.edu/tgle/vol48/iss3/2 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 2015 THE GREAT LAKES ENTOMOLOGIST 1111Department of Biology, Alma College, Alma, MI 48801.*Corresponding author: (e-mail: rroeper@yahoo.com).Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central MichiganRichard A. Roeper1,*, Mark A. Bunce1, John E. Harlan1, and Richard G. Bowker1AbstractXyleborus affinis Eichhoff colonized wind thrown timber in the moist floodplain habitats of Central Michigan.  Single adult females constructed a complex gallery system consisting of phloem–sapwood interface tunnels and sapwood tunnels.  An average of 24 progeny adults and a sex ratio of 14 females to 1 male were found in mature galleries after the first of September. ____________________Xyleborus affinis Eichhoff (Coleoptera: Curculionidae: Scolytinae) has a pan-tropical distribution infesting some 300 woody hosts (Schedl 1963, Wood 1982, Rabaglia et al. 2006).  Wood (1982) considered the beetle to be tropical American in origin, and it is distributed from Florida north to Massachusetts and west to Michigan, Missouri, and Texas within the USA.  The beetle has extended its range or has been introduced into Africa, Hawaii, and Southeast Asia through New Guinea and some Pacific islands.  Bright (1968) listed the gen-era Betula, Carya, Castanea, Celtis, Diosypra, Liquidambar, Mimosa, Quercus and Robinia as temperate tree hosts. Schneider (1987) listed Fraxinus. Schedl (1963) provided observation of beetle’s habits in Africa under the synonym X. mascarensis Eichhoff.  Roeper et al. (1980a and b) cultured the beetle using in vitro techniques and provided life cycle observations.  This study reports on the natural habits of X. affinis infesting deciduous woody hosts in Central Michigan.MethodsThese observations were made over three decades from the mid-1970s to the 1990s during the collection of live beetle specimens for use in vitro culture studies.  The study areas were the Pine River floodplains near the village of Sumner, Gratiot County, Michigan.  Overall 32 host logs were collected and returned to the laboratory.  Within days each collected bole was cut into disks and then carefully dissected using wood chisels.  Eighty-eight complete galleries and 77 partial galleries of X. affinis were dissected for this study.  Life stages of X. affinis and measurements of tunnel lengths were recorded.Results and DiscussionHost Characteristics.  Xyleborus affinis primarily attacked wind-thrown silver maples boles (Acer saccharinum L.) (N = 29) in the moist floodplain for-ests and river habitats in central Michigan.  The prone trees were found over standing water of temporary ponds or flowing water of the river.  On some oc-casions the bole of the silver maple was partly submerged in the river water. These observations suggest the beetles preferred a high moisture and/or high relative humidity environment.  The boles of the host trees were horizontal and uprooted, yet often had live leaves existing on lateral branches.  On two occa-1Roeper et al.: Observations of Xyleborus affinis Eichhoff (Coleoptera:CurculioniPublished by ValpoScholar, 2015112 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4sions X. affinis were observed on wind- thrown northern red oak (Quercus rubra L.) and once on a wind-thrown ash (Fraxinus sp.).  Acer is recorded as host for this beetle here for the first time.  The beetle was never found in wind- thrown trees in adjacent, upland, non–floodplain habitats after three years of study.Host Colonization Patterns.  Similarly to other Xyleborus species, only the adult females fly to infest new host material.  In Gratiot County only a single colonization period was observed with the earliest attacks beginning in mid-May and continuing to mid-June.  The density of attack entrance attack holes averaged 25.2 per dm2 (SE = 3.7, N = 16), ranging from 11.3 to 41.0 entrance holes per dm2 on the surface of the maple boles.Gallery Characteristics.  Schedl (1963) speculated that two or more females would cooperate in the construction of a gallery system.  We found no evidence supporting Schedl’s hypothesis based on these Michigan observations. Single foundress females constructed each gallery system.  The boring frass produced by the female adult was granular sawdust of woody material pushed out the beetle’s entrance hole.Among developed gallery systems (N = 69) we observed that within 53 galleries (76.8%) the adult females bored through the bark and constructed a lateral tunnel at the phloem-sapwood interface.  These laterals are always straight and constructed perpendicular to the length of the longitudinal axis of the host bole in contrast to Schedl (1963) who described these phloem-sapwood laterals as curving and joining other similar laterals.  In 36 galleries (52%) the phloem-sapwood laterals were constructed in one direction from the entrance. In 17 (24.6%), phloem–sapwood laterals were constructed in two directions from the entrance.  The average length of these phloem-sapwood lateral galleries was 28mm (SE = 2.8, N = 53) and ranged from 4.0 to 49.0 mm in length.  The phloem-sapwood laterals appear to be an unusual characteristic compared with other ambrosia beetle species that usually excavate tunnels directly into the sapwood.  Xyleborus ferrugineous F.  (Wood 1962) and X. seriatus  Brandford (Hoebeke and Rabaglia 2008) also construct phloem-sapwood galleries.  Schedl (1963) speculated that the construction of these tunnels provided supplementary nutrition to the beetle’s normal xylomycetophagous habit found in the sapwood tunnels.  The lateral tunnel constructed at the phloem-sapwood interface rarely varied in depth.  Occasionally along their length there were short segments that were burrowed 2 to 3 mm into the outer most portion of the sapwood xylem. These phloem–sapwood laterals never extended deeper into the sapwood.  The adult females were observed ovipositing two to four eggs at the end of the phloem interface tunnels in only three of 43 galleries.Sixteen (23.2%) of the mature galleries lacked phloem-sapwood lateral galleries, and all the gallery systems tunnels were further constructed into the sapwood, as is typical of ambrosia beetles.  The sapwood tunnels were at first usually constructed perpendicular to the outer surface of the host near the ini-tial entrance hole of the female adult.  The tunnels constructed to a particular depth into the sapwood then each curved laterally, not always following a growth ring.  Further penetration into the sapwood led to the construction of as many as six secondary or tertiary lateral sapwood tunnels that usually curved toward the heartwood.  The fungal symbionts failed to cause dark staining of the wood around the galleries that is generally typical of ambrosia beetle gallery systems. The sapwood galleries during June averaged 39.3 mm in length (SE = 1.8; N = 29) and ranged from 21 to 65mm.  During July to mid August the sapwood tunnels averaged 70.3 mm in length (SE = 1.7, N = 22) and ranged from 60 to 91 mm.  In mid August galleries were mature with a mean length of 112 mm (SE = 5.6, N = 37) and ranging from 82 to 163 mm long since boring activity had ceased, evidenced by the lack of fresh boring frass.Progeny.  From dissection of galleries though the summer period, eggs were observed from mid-June to late July.  Larvae were found from mid-June to 2The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 2https://scholar.valpo.edu/tgle/vol48/iss3/22015 THE GREAT LAKES ENTOMOLOGIST 113mid-August and pupae from late July to late August.  The larvae appeared to be mycetophagous because they were not involved in the enlargement of the gallery system.  The first teneral adults were observed in late July.  The approximate time of development from egg to adult was 5.5 to 7 weeks.  The teneral adults overwintered in their parental gallery system.  From mature gallery systems after the first of September the number of progeny adults averaged 24.0 per gallery (SE = 0.61, N = 22) and ranged from to 17 to 41.  The sex ratio was found to be 14 females to 1 male (493 females to 35 males from 22 galleries).We observed only a single generation breeding in each particular log. However, when X. affinis females were removed from their gallery system and cultured in vitro, they did not exhibit any reproductive diapause and constructed gallery systems and oviposited in culture media (Roeper et al. 1980a, 1980b). We never observed progeny adults using an old parental gallery system for a second breeding season as suggested by Schedl (1963) in Africa and Schneider (1987) in Kansas.  Seasonal changes may account for the differences in X. affinis’ gallery habits observed in this study.AcknowledgmentsWe thank Antony I. Cognato of Michigan State University for his helpful comments on this manuscript.Literature CitedBright, D. E.  1968.  Review of the Tribe Xyleborini in America North of Mexico (Cole-optera: Scolytidae). Canadian Entomologist100: 1288-1322.Hoebeke, E. R., and R. J. Rabaglia.  2008.  Xyleborus seriatus Blandford (Coleoptera: Curculionidae:Scolytinae), An Asian Ambrosia Beetle New to North America. Pro-ceeding of the Entomological Society of Washington. 110: 470-476.Rabaglia, R. J., S. A. Dole, and A. I. Cognato.  2006.  Review of Xyleborina (Coleop-tera: Curculiondae:Scolytinae) Occurring North of Mexico, with an Illustrated Key. Annals of the Entomological Society of America. 99: 1034-1056.Roeper, R. A., L. M. Treeful, R. A. Foote, and M. A. Bunce.  1980a.  In vitro culture of the ambrosia beetle Xyleborus affinis (Coleoptera: Scolytidae). The Great Lakes Entomologist. 13:33-35.Roeper, R. A., L. M. Treeful, K. O’Brien, R. A. Foote, and M. A. Bunce.  1980b.  Life history of Xyleborus affinis (Coleoptera: Scolytidae) from in vitro culture.  The Great Lakes Entomologist. 13:141-143.Schedl, K. E.  1963.  Scolytidae und Platypodidae Afrikas. BandII,  Revista de Mocam-bique 5: 1-594.Schneider, I.  1987.  Distribution, fungus–transfer and gallery construction of the ambrosia beetle Xyleborus affinis in comparison with X. mascarensis (Coleoptera: Scolytidae). Entomologia Generalis. 12: 267-275. Wood, Stephen L.  1982.  The Bark and Ambrosia beetles of North and Central America (Coleoptera: Scolytidae), a Taxonomic Monograph. Great Basin Naturalist Memoirs. 6:1-1359.3Roeper et al.: Observations of Xyleborus affinis Eichhoff (Coleoptera:CurculioniPublished by ValpoScholar, 2015

Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central Michigan

ValpoScholar

The Great Lakes Entomologist 
Volume 48 
Numbers 3/4 -- Fall/Winter 2015 Numbers 3/4 -- 
Fall/Winter 2015 
Article 2 
October 2015 
Observations of Xyleborus affinis Eichhoff 
(Coleoptera:Curculionidae:Scolytinae) in Central Michigan 
Richard A. Roeper 
Alma College, rroeper@yahoo.com 
Mark A. Bunce 
Alma College 
John E. Harlan 
Alma College 
Richard G. Bowker 
Alma College 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Roeper, Richard A.; Bunce, Mark A.; Harlan, John E.; and Bowker, Richard G. 2015. "Observations of 
Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central Michigan," The Great Lakes 
Entomologist, vol 48 (3) 
Available at: https://scholar.valpo.edu/tgle/vol48/iss3/2 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
2015 THE GREAT LAKES ENTOMOLOGIST 111
1Department of Biology, Alma College, Alma, MI 48801.
*Corresponding author: (e-mail: rroeper@yahoo.com).
Observations of Xyleborus affinis Eichhoff 
(Coleoptera:Curculionidae:Scolytinae) in Central Michigan
Richard A. Roeper1,*, Mark A. Bunce1, John E. Harlan1, and Richard G. Bowker1
Abstract
Xyleborus affinis Eichhoff colonized wind thrown timber in the moist 
floodplain habitats of Central Michigan.  Single adult females constructed a 
complex gallery system consisting of phloem–sapwood interface tunnels and 
sapwood tunnels.  An average of 24 progeny adults and a sex ratio of 14 females 
to 1 male were found in mature galleries after the first of September.
 
____________________
Xyleborus affinis Eichhoff (Coleoptera: Curculionidae: Scolytinae) has a 
pan-tropical distribution infesting some 300 woody hosts (Schedl 1963, Wood 
1982, Rabaglia et al. 2006).  Wood (1982) considered the beetle to be tropical 
American in origin, and it is distributed from Florida north to Massachusetts 
and west to Michigan, Missouri, and Texas within the USA.  The beetle has 
extended its range or has been introduced into Africa, Hawaii, and Southeast 
Asia through New Guinea and some Pacific islands.  Bright (1968) listed the gen-
era Betula, Carya, Castanea, Celtis, Diosypra, Liquidambar, Mimosa, Quercus 
and Robinia as temperate tree hosts. Schneider (1987) listed Fraxinus. Schedl 
(1963) provided observation of beetle’s habits in Africa under the synonym X. 
mascarensis Eichhoff.  Roeper et al. (1980a and b) cultured the beetle using in 
vitro techniques and provided life cycle observations.  This study reports on the 
natural habits of X. affinis infesting deciduous woody hosts in Central Michigan.
Methods
These observations were made over three decades from the mid-1970s to 
the 1990s during the collection of live beetle specimens for use in vitro culture 
studies.  The study areas were the Pine River floodplains near the village of 
Sumner, Gratiot County, Michigan.  Overall 32 host logs were collected and 
returned to the laboratory.  Within days each collected bole was cut into disks 
and then carefully dissected using wood chisels.  Eighty-eight complete galleries 
and 77 partial galleries of X. affinis were dissected for this study.  Life stages 
of X. affinis and measurements of tunnel lengths were recorded.
Results and Discussion
Host Characteristics.  Xyleborus affinis primarily attacked wind-thrown 
silver maples boles (Acer saccharinum L.) (N = 29) in the moist floodplain for-
ests and river habitats in central Michigan.  The prone trees were found over 
standing water of temporary ponds or flowing water of the river.  On some oc-
casions the bole of the silver maple was partly submerged in the river water. 
These observations suggest the beetles preferred a high moisture and/or high 
relative humidity environment.  The boles of the host trees were horizontal and 
uprooted, yet often had live leaves existing on lateral branches.  On two occa-
1
Roeper et al.: Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculioni
Published by ValpoScholar, 2015
112 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4
sions X. affinis were observed on wind- thrown northern red oak (Quercus rubra 
L.) and once on a wind-thrown ash (Fraxinus sp.).  Acer is recorded as host for 
this beetle here for the first time.  The beetle was never found in wind- thrown 
trees in adjacent, upland, non–floodplain habitats after three years of study.
Host Colonization Patterns.  Similarly to other Xyleborus species, only 
the adult females fly to infest new host material.  In Gratiot County only a single 
colonization period was observed with the earliest attacks beginning in mid-
May and continuing to mid-June.  The density of attack entrance attack holes 
averaged 25.2 per dm2 (SE = 3.7, N = 16), ranging from 11.3 to 41.0 entrance 
holes per dm2 on the surface of the maple boles.
Gallery Characteristics.  Schedl (1963) speculated that two or more 
females would cooperate in the construction of a gallery system.  We found no 
evidence supporting Schedl’s hypothesis based on these Michigan observations. 
Single foundress females constructed each gallery system.  The boring frass 
produced by the female adult was granular sawdust of woody material pushed 
out the beetle’s entrance hole.
Among developed gallery systems (N = 69) we observed that within 53 
galleries (76.8%) the adult females bored through the bark and constructed 
a lateral tunnel at the phloem-sapwood interface.  These laterals are always 
straight and constructed perpendicular to the length of the longitudinal axis of 
the host bole in contrast to Schedl (1963) who described these phloem-sapwood 
laterals as curving and joining other similar laterals.  In 36 galleries (52%) the 
phloem-sapwood laterals were constructed in one direction from the entrance. 
In 17 (24.6%), phloem–sapwood laterals were constructed in two directions from 
the entrance.  The average length of these phloem-sapwood lateral galleries 
was 28mm (SE = 2.8, N = 53) and ranged from 4.0 to 49.0 mm in length.  The 
phloem-sapwood laterals appear to be an unusual characteristic compared with 
other ambrosia beetle species that usually excavate tunnels directly into the 
sapwood.  Xyleborus ferrugineous F.  (Wood 1962) and X. seriatus  Brandford 
(Hoebeke and Rabaglia 2008) also construct phloem-sapwood galleries.  Schedl 
(1963) speculated that the construction of these tunnels provided supplementary 
nutrition to the beetle’s normal xylomycetophagous habit found in the sapwood 
tunnels.  The lateral tunnel constructed at the phloem-sapwood interface rarely 
varied in depth.  Occasionally along their length there were short segments that 
were burrowed 2 to 3 mm into the outer most portion of the sapwood xylem. 
These phloem–sapwood laterals never extended deeper into the sapwood.  The 
adult females were observed ovipositing two to four eggs at the end of the phloem 
interface tunnels in only three of 43 galleries.
Sixteen (23.2%) of the mature galleries lacked phloem-sapwood lateral 
galleries, and all the gallery systems tunnels were further constructed into the 
sapwood, as is typical of ambrosia beetles.  The sapwood tunnels were at first 
usually constructed perpendicular to the outer surface of the host near the ini-
tial entrance hole of the female adult.  The tunnels constructed to a particular 
depth into the sapwood then each curved laterally, not always following a growth 
ring.  Further penetration into the sapwood led to the construction of as many 
as six secondary or tertiary lateral sapwood tunnels that usually curved toward 
the heartwood.  The fungal symbionts failed to cause dark staining of the wood 
around the galleries that is generally typical of ambrosia beetle gallery systems. 
The sapwood galleries during June averaged 39.3 mm in length (SE = 1.8; N 
= 29) and ranged from 21 to 65mm.  During July to mid August the sapwood 
tunnels averaged 70.3 mm in length (SE = 1.7, N = 22) and ranged from 60 to 
91 mm.  In mid August galleries were mature with a mean length of 112 mm 
(SE = 5.6, N = 37) and ranging from 82 to 163 mm long since boring activity 
had ceased, evidenced by the lack of fresh boring frass.
Progeny.  From dissection of galleries though the summer period, eggs 
were observed from mid-June to late July.  Larvae were found from mid-June to 
2
The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 2
https://scholar.valpo.edu/tgle/vol48/iss3/2
2015 THE GREAT LAKES ENTOMOLOGIST 113
mid-August and pupae from late July to late August.  The larvae appeared to be 
mycetophagous because they were not involved in the enlargement of the gallery 
system.  The first teneral adults were observed in late July.  The approximate 
time of development from egg to adult was 5.5 to 7 weeks.  The teneral adults 
overwintered in their parental gallery system.  From mature gallery systems 
after the first of September the number of progeny adults averaged 24.0 per 
gallery (SE = 0.61, N = 22) and ranged from to 17 to 41.  The sex ratio was found 
to be 14 females to 1 male (493 females to 35 males from 22 galleries).
We observed only a single generation breeding in each particular log. 
However, when X. affinis females were removed from their gallery system and 
cultured in vitro, they did not exhibit any reproductive diapause and constructed 
gallery systems and oviposited in culture media (Roeper et al. 1980a, 1980b). 
We never observed progeny adults using an old parental gallery system for a 
second breeding season as suggested by Schedl (1963) in Africa and Schneider 
(1987) in Kansas.  Seasonal changes may account for the differences in X. affinis’ 
gallery habits observed in this study.
Acknowledgments
We thank Antony I. Cognato of Michigan State University for his helpful 
comments on this manuscript.
Literature Cited
Bright, D. E.  1968.  Review of the Tribe Xyleborini in America North of Mexico (Cole-
optera: Scolytidae). Canadian Entomologist100: 1288-1322.
Hoebeke, E. R., and R. J. Rabaglia.  2008.  Xyleborus seriatus Blandford (Coleoptera: 
Curculionidae:Scolytinae), An Asian Ambrosia Beetle New to North America. Pro-
ceeding of the Entomological Society of Washington. 110: 470-476.
Rabaglia, R. J., S. A. Dole, and A. I. Cognato.  2006.  Review of Xyleborina (Coleop-
tera: Curculiondae:Scolytinae) Occurring North of Mexico, with an Illustrated Key. 
Annals of the Entomological Society of America. 99: 1034-1056.
Roeper, R. A., L. M. Treeful, R. A. Foote, and M. A. Bunce.  1980a.  In vitro culture 
of the ambrosia beetle Xyleborus affinis (Coleoptera: Scolytidae). The Great Lakes 
Entomologist. 13:33-35.
Roeper, R. A., L. M. Treeful, K. O’Brien, R. A. Foote, and M. A. Bunce.  1980b.  Life 
history of Xyleborus affinis (Coleoptera: Scolytidae) from in vitro culture.  The Great 
Lakes Entomologist. 13:141-143.
Schedl, K. E.  1963.  Scolytidae und Platypodidae Afrikas. BandII,  Revista de Mocam-
bique 5: 1-594.
Schneider, I.  1987.  Distribution, fungus–transfer and gallery construction of the 
ambrosia beetle Xyleborus affinis in comparison with X. mascarensis (Coleoptera: 
Scolytidae). Entomologia Generalis. 12: 267-275. 
Wood, Stephen L.  1982.  The Bark and Ambrosia beetles of North and Central America 
(Coleoptera: Scolytidae), a Taxonomic Monograph. Great Basin Naturalist Memoirs. 
6:1-1359.
3
Roeper et al.: Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculioni
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Observations of Xyleborus affinis Eichhoff (Coleoptera:Curculionidae:Scolytinae) in Central Michigan

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