Identify Common

Nitidulid Beetles

Associated with Oak

Wilt Mats in Minnesota

North Central

Research Station

Prepared by

Forest Service

HOW to

2001 HT-71
The Authors

Valerie J. Cervenka, Thomas C. Skalbeck, John

F. Kyhl, Darren C. Blackford, Jennifer J. Juzwik,

and Steven J. Seybold

Acknowledgments

We thank S.A. Katovich (USDA Forest Service)

R.J. Bartelt (USDA Agricultural Research

Service) and R.W. Holzenthal (University of

Minnesota) for review and suggestions. Specimens used in this study were deposited in the

University of Minnesota Insect Collection.

Funding for this research was provided by the

Minnesota Environment and Natural Resources

Trust Fund as recommended by the Legislative

Commission on Minnesota Resources and by

USDA Multistate Project W-189.

Cover photos:

Top left: Nitidulid eggs on a mature oak wilt mat

collected during midspring.

Center: Nitidulid larva: Epuraea corticina

Erichson.

Bottom left: Nitidulid adult: Glischrochilus

sanguinolentus (Olivier).

Illustrations by:

The authors are grateful to Julie Martinez for her

expert drawings of nitidulid larvae.
HOW to

Identify Common Nitidulid

Beetles Associated with Oak

Wilt Mats in Minnesota

Contents Page

Purpose .................................................... i

Introduction ............................................ 1

Characteristics of General

 Nitidulid Adult ...................................... 2

Characteristics of General

 Nitidulid Larva ..................................... 3

Species Descriptions ............................. 4

 Carpophilus sayi Parsons .......................... 4

 Colopterus truncatus Randall ..................... 5

 Epuraea corticina Erichson ........................ 6

 Glischrochilus fasciatus (Olivier) ................ 7

 Glischrochilus quadrisignatus (Say) ........... 8

 Glischrochilus sanguinolentus (Olivier) ...... 9

References ............................................. 10

Glossary ................................................. 11
Purpose

We developed this handbook for forestry professionals, land managers, and homeowners to help them

identify the most common adult and larval sap

beetles found in oak wilt mats in the North Central

States. Although the photographs depict the natural

color of adults, preserved specimens may not have

exactly the same color as those in the pictures. All

sizes given are length ranges and mean lengths based

on measurements of our specimens using a light

microscope with an ocular micrometer. The brief

written descriptions are not intended to be taxonomically complete, but to pinpoint the features most

useful in distinguishing species from one another.

The descriptions are largely based on those of

Parsons (1943).

i
Introduction

Oak wilt, caused by the fungus Ceratocystis

fagacearum (Bretz) Hunt, is an important disease of

oaks throughout the Eastern United States. Thousands

of native oaks, particularly those in the red oak group

(Section Lobatae = Erythrobalanus), succumb to the

disease each year across the Midwest. The pathogen

is spread in two ways: underground through root

grafts and overland by insect vectors. Insect transmission is the primary means of establishing new oak

wilt infection centers, and the principal vectors in the

North Central States are sap beetles (Coleoptera:

Nitidulidae) (Juzwik 2001). Although there are many

nitidulid species associated with oaks, six species

make up the majority of those typically collected

from oak wilt mats in Minnesota (Cease and Juzwik

2001), Wisconsin (McMullen et al. 1960), and Illinois

(Himelick and Curl 1958). These species are

Carpophilus sayi Parsons, Colopterus truncatus

Randall, Epuraea corticina Erichson, Glischrochilus

fasciatus (Olivier), G. quadrisignatus (Say), and G.

sanguinolentus (Olivier). Carpophilus sayi and

Colopterus truncatus are the predominant species

collected from fresh wounds on red oak trees in

Minnesota (Juzwik et al. 1999), making these two

nitidulids the primary vector species in this State. Of

the six nitidulid species, Carpophilus sayi is more

abundant in oak wilt mats in the spring than in the

fall, the three Glischrochilus species are more

abundant in oak wilt mats in the fall than in the

spring, whereas, Colopterus truncatus and Epuraea

corticina are similarly abundant in oak wilt mats in

the spring and fall.

1
Adult sap beetles are generally small (~2 to 12 mm

long) with flattened and broadly oval to somewhat

elongate bodies (see A below). The body color of the

adults ranges from reddish brown to black, in some

cases with red, orange, or yellow patterns on the

elytra (wing covers). Certain species have short

elytra that expose the upper surface of the last two or

three abdominal segments. Adult sap beetles are

distinguished from other beetles visiting oak wilt

mats by having 11-segmented antennae that end in a

3-segmented, ball-like club (B). Adults are attracted

to and live in fermenting plant sap, decaying fruit, or

fungi (Downie and Arnett 1996).

Adult sap beetle, Glischrochilus fasciatus (A) and

enlarged 11-segmented right antenna showing the 3-

segmented club (B).

2

Characteristics of General Nitidulid Adult
Larval sap beetles are elongate and cylindrical, range

from ~3 to 8 mm in length, and have three pairs of

well-developed thoracic legs (see below). The first

thoracic tergum (hardened plate on upper surface of

the body segment bearing the first pair of legs) is

usually pigmented, but in some species terga on both

the thorax and abdomen are pigmented. The ninth

abdominal tergum is especially important for

identifying the larvae. This tergum usually has paired

urogomphi (fixed, hornlike structures) that may be

simple or branched and often have paired pregomphi

located anteriorly (in front of them).

Larval sap beetle, Epuraea corticina, showing (A)

dorsal view with plate-like and pigmented thoracic

and abdominal terga (TT and AT) and urogomphi (U)

on the last abdominal tergum. Thoracic legs (TL) are

evident in (B) the lateral view.

3

Characteristics of General Nitidulid Larva
Carpophilus sayi Parsons

Adults: Small (3.5 to 5.1 mm, mean = 4.2 mm, n =

15), very dark brown to black, sometimes with

pronotum (shoulders) and pronotal margins rufous

(pale red). Sparsely pubescent (“fuzzy”) and punctate.

Elytra short, revealing last two abdominal segments.

Nearly perpendicular angle formed by median suture

(line where two elytra meet) and tip of elytron (see A

below). For comparison, an obtuse angle is formed by

median suture and tip of elytron in Colopterus

truncatus (see B below).

4

Larvae: Length, based on

one specimen, 4.2 mm.

Very similar to Colopterus

truncatus, but pregomphi

are longer, and the space

between urogomphi is more

angular or deeply truncate.

Species Descriptions
Colopterus truncatus Randall

Adults: Very small (1.9 to 2.6 mm, mean = 2.2 mm,

n = 24), medium brown, sparsely pubescent; head,

pronotum, and elytra punctate; elytra short, revealing

last three abdominal segments (A, dorsal view).

Obtuse angle formed by median suture and tip of

elytron (see B on previous page). Lateral view (B, this

page) illustrates how extremely flattened adult

Colopterus truncatus can be.

Larvae: Length 3.2 to 5.3

mm. Body entirely creamy

white. Head and prothorax

sclerotized (hardened) and

golden brown. Ninth abdominal segment sclerotized

dorsally, with one small pair

of pregomphi and one pair

unbranched urogomphi.

5
Epuraea

corticina

Erichson

Adults: Small (2.8 to 4.0 mm, mean = 3.3 mm, n =

29), oblong, brownish yellow, mottled with dark

brown; pronotum usually with acute hind angles;

elytra covering all but last abdominal segment.

Larvae: Length, 4.8 to 5.9

mm. Body mostly creamy

white. Head golden brown.

Body appears to have dorsal

horizontal stripes, caused by

debris trapped in the tubercles

on the dorsum of each

segment. Ninth abdominal

segment with two pair of

small, straight urogomphi and

numerous tubercles from

which setae (single small

hairs) protrude.

6
The following species of Glischrochilus are relatively

large, oblong, shiny sap beetles. Those described here

are attractively marked dorsally (on top) with yellow,

yellow-orange, or red. The elytra leave only the tip of

the last abdominal segment exposed. Glischrochilus

spp. are common in a variety of habitats other than

oak wilt mats. Their presence in oak woodlands is not

necessarily an indication of oak wilt.

Glischrochilus

fasciatus (Olivier)

Adults: Medium to large (4.2 to 6.6 mm, mean = 5.6

mm, n = 26), head and pronotum black. Elytra black

with large, paired yellow blotches that are symmetrical relative to the median suture. The yellow blotches

located anteriorly (toward the head) are tri-lobed.

Larvae: Unknown.

7
Glischrochilus quadrisignatus (Say)

Adults: Medium to large (3.9 to 6.7 mm, mean = 5.2

mm, n = 28). Glischrochilus quadrisignatus can be

distinguished from G. fasciatus in two ways: the

yellow elytral blotches are smaller, and the anterior

blotches are farther from the median suture than the

posterior (rear) blotches.

Larvae: Similar to G. sanguinolentus (Connell

1991).

8
Glischrochilus sanguinolentus (Olivier)

Adults: Medium to large (4.4 to 6.4 mm, mean =

5.2 mm, n = 20); elytra red with black submedian

spot and black apical one-third.

Larvae: Length, based on two specimens, 7.9 to 8.4

mm. Body mostly creamy white and somewhat

flattened. Head, pronotum, and ninth abdominal

segment golden brown. Abdominal spiracles protrude, increasing in length down the body, and are

golden brown at the tips. Ninth abdominal segment

with one pair pregomphi and one pair branched

urogomphi.

9
References

Cease, K.R.; Juzwik, J. 2001. Predominant nitidulid

species (Coleoptera: Nitidulidae) associated with

spring oak wilt mats in Minnesota. Canadian

Journal of Forest Research. 31: 635-643.

Connell, W.A. 1991. Insect and mite pests in food, an

illustrated key. Vol. 2. Sap beetles (Nitidulidae,

Coleoptera). Agric. Handb. 655. Washington, DC:

U.S. Department of Agriculture, Forest Service:

151-174.

Downie, N.M.; Arnett, R.H., Jr. 1996. The beetles of

northeastern North America, Volume II: Polyphaga,

Superfamily Bostrichoidea thru Curculionoidea.

Gainesville, FL: The Sandhill Crane Press.

 Himelick, E.B.; Curl, E.A. 1958. Transmission of

Ceratocystis fagacearum by insects and mites. Plant

Disease Report. 42: 538-540.

Juzwik, J. 2001. Overland transmission of

Ceratocystis fagacearum: extending our understanding. In: Shade tree wilt diseases. St. Paul, MN:

American Phytopathological Society, APS Press.

Chapter 8.

Juzwik, J.; Skalbeck, T.C.; Neuman, M.F. 1999.

Nitidulid species associated with fresh wounds on

red oaks during spring in Minnesota. Phytopathology. 89: S38.

McMullen, L.H.; Shenefelt, R.D.; Kuntz, J.E. 1960. A

study of insect transmission of oak wilt in Wisconsin. Wisconsin Academy of Sciences, Arts and

Letters. 49: 73-84.

Parsons, C.T. 1943. A revision of the nearctic

Nitidulidae (Coleoptera). Bulletin of the Museum of

Comparative Zoology. 92: 121-278.

10
11

Glossary

Abdomen.—The third or posterior division of the

insect body; consists normally of 9 or 10 apparent

segments; bears no functional legs in the adult

stage.

Anterior.—In front; before; having to do with the

forward section of something.

Apical.—At, near, or pertaining to the apex, which is

that part of any joint or segment opposite the base

by which it is attached. For example, that point of

a wing furthest removed from the base or at the

end.

Dorsal.—Of or belonging to the upper surface.

Elytron/Elytra.—The anterior leathery or chitinous

wings of beetles, serving as coverings to the hind

wings, commonly meeting in a straight line down

the middle of the body when the beetle is at rest

and not flying.

Larva/Larvae.—A young insect that quits the egg in

an early stage of development and differs fundamentally in form from the adult. The immature

form of animals that undergo metamorphosis;

other related terms are nymph, caterpillar, slug,

maggot, and grub.

Lateral.—Relating, pertaining, or attached to the

side.

Posterior.—In the rear; after; having to do with the

hind section of something; opposite of anterior.

Pronotum.—The upper or dorsal surface of the

prothorax.

Prothorax.—The first thoracic ring or segment; it

bears the anterior legs but no wings in adult

insects.
Pubescent.—Downy; clothed with soft, short, fine

closely set hair.

Punctate.—Having impressed points or punctures.

Root graft.—Roots that have grown together so that a

graft union is made between the conducting tissues

of both roots. The oak wilt pathogen can move

through grafted roots between infected and healthy

trees to cause new infections.

Rufous.—Pale red.

Sclerite.—Any piece of the insect body wall bounded

by sutures. Sclerotization is the hardening of the

insect body wall by the deposition of sclerotizing

substances.

Seta/Setae.—Hairs or bristles that are hollow structures developed as extensions of the insect epidermis.

Spiracles.—Breathing pores or openings in the sides

of the insect body through which air enters the

body.

Submedian.—Below a line drawn through the middle

of a structure or animal.

Tergite.—A dorsal sclerite or part of a segment,

especially when such part consists of a single

sclerite or plate.

Tergum/Terga.—The upper or dorsal surface of any

body segment of an insect, whether it consists of

one or more than one sclerite or plate.

Thorax/Thoraces.—The second or intermediate

region of the insect body bearing the true legs and

wings, made up of three rings, named in order, pro-,

meso-, and metathorax. As adjective, thoracic.

Truncate.—Cut off squarely at the tip.

12
Tubercles.—Little solid pimples or small buttons on

the surface of the insect body, sometimes bearing

setae or bristles.

Urogomphus/Urogomphi.—Fixed or mobile

structure found on the terminal segments of certain

larval insects. Pregomphi are related structures that

are generally smaller and are located anterior to the

urogomphi.

Vector.—An organism such as an insect, mite,

nematode, or a higher animal such as a bird or

rodent that carries a pathogenic agent to a susceptible host.

Companion Publications

Pokorny, J. 1999. How to collect field samples and

identify the oak wilt fungus in the laboratory.

NA-FR-01-99. St. Paul, MN: U.S. Department of

Agriculture, Forest Service, Northeastern Area

State and Private Forestry. 12 p.

O’Brien, J.G.; Mielke, M.E.; Starkey, D.; Juzwik, J.

2000. How to identify, prevent, and control oak

wilt. NA-PR-03-00. St. Paul, MN: U.S. Department of Agriculture, Forest Service, Northeastern

Area State and Private Forestry. 28 p.

13
Additional Notes
The U.S. Department of Agriculture (USDA) prohibits

discrimination in all its programs and activities on the basis

of race, color, national origin, gender, religion, age, disability,

political beliefs, sexual orientation, and marital or family

status. (Not all prohibited bases apply to all programs.)

Persons with disabilities who require alternative means for

communication of program information (Braille, large print,

audiotape, etc.) should contact USDA’s TARGET Center at

(202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director,

Office of Civil Rights, Room 326-W, Whitten Building, 14th

and Independence Avenue, SW, Washington, DC 20250-

9410, or call (202) 720-5964 (voice or TDD). USDA is an

equal opportunity provider and employer.
For more information, contact:

Steven Seybold, Assistant Professor

Departments of Entomology and Forest Resources

219 Hodson Hall

1980 Folwell Ave.

University of Minnesota

St. Paul, MN 55108-6125

(612) 624-3715

e-mail: sseybold@tc.umn.edu

http://www.entomology.umn.edu

Jennifer Juzwik, Project Leader

North Central Research Station

USDA Forest Service

1992 Folwell Ave.

St. Paul, MN 55108

(651) 649-5114

e-mail:jjuzwik@fs.fed.us

http://www.ncrs.fs.fed.us

Copies available from—

North Central Research Station

1992 Folwell Avenue

St. Paul, MN 55108

North Central Distribution Center

Forest Products Laboratory

One Gifford Pinchot Drive

Madison, WI 53705

Available on the web at:

http://www.na.fs.fed.us/spfo

 OR

http://www.ncrs.fs.fed.us

HT-71