Emerald Ash Borer
Agrilus planipennisFairmaire
(Coleoptera: Buprestidae)
A guide to identification and
comparison to similar species
Prepared by:
Gary L. Parsons
Department of Entomology, Michigan State University
November 2008
Introduction The adult stage of the Emerald Ash Borer (EAB) is fairly distinctive
and usually easy to tell apart from most similarly colored and shaped
buprestids and other insects by a trained taxonomist. However, many
researchers and field workers currently sampling for EAB are not
trained taxonomists, and might confuse some other similarly shaped
or colored insects with EAB. The species included in this guide were
chosen because of their relative commonness, similarity in size,
shape and/or coloration to the EAB, and because specimens were
available for photography in the A.J. Cook Arthropod Research
Collection, at Michigan State University. Additional species, not
included here, may be present in other parts of North America that
could also potentially be confused with the EAB.
How to Use This Guide
This guide is intended to assist insect diagnosticians and others
who have some familiarity in identifying insects. It’s use will be
easier if the user has at least a basic knowledge of insect
morphology and terminology and a basic familiarity with insect
orders, families, and genera.
The main purpose of this guide is to assist with sight identification of
adult specimens that have been field collected or reared. It will be
somewhat easier to verify the identity of beetles reared from known
hosts, however host data is not necessary to use this simple guide.
Many trapping methods for EAB utilize Tanglefoot®, Pest-Stick® or
some other kind of sticky material. To be able to properly identify
specimens, all residues of this sticky material must be removed with a
suitable cleaning agent. Soaking beetles in 95% ethanol will dissolve
Tanglefoot, and Histoclear® will dissolve Pest-Stick. It may take
several days of soaking and frequent transfers to clean solvent to
remove all traces of the sticky material. In addition, specimens in
alcohol usually do not appear their true color or show setae and setal
patterns while wet. Ideally, specimens should be cleaned and allowed
to air dry. Specimens mounted on pins or points will usually be much
easier to manipulate under a dissecting microscope, which is usually
needed for best examination of these small beetles. The bright lighting
typically used with microscopy will best reflect the coloration of these
beetles for comparison to the pictures used in the guide.
Note the similarity in color among the beetles in the photos to the left that were
removed from sticky traps and pinned without any cleaning. The photos to the
right are the same beetles after cleaning for only a few seconds with hexane
used as a solvent. While still not perfectly clean, sufficient color and patterns
now are evident to allow these to be identified to species.
Agrilus
anxius
Agrilus
bilineatus
Agrilus
cyanescens
The initial pages of this guide describe the general characteristics for
identification of the emerald ash borer. These are followed by pages showing
some additional species of Agrilus, other Buprestidae, and a few other beetles
that have similar color and/or shape to the EAB, and which could potentially
be confused with it.
These pages can be used for basic sight comparison and possible
identification of some of the more common species in question. This guide
uses coloration differences and a few distinctive, morphological characters for
comparisons. Those using this guide should not expect to be able to identify
any given specimen with absolute certainty to the species level. There are
171 species of Agrilusin North America, and only a few representatives are
shown here. Many of the smaller species are very similar to each other, and
most can only be reliably identified with keys. There are a few keys for North
American Agrilus
(Fisher 1928, Bright 1987, Downie & Arnett 1996 for eastern species)
and
other Buprestidae that can be used for identification of difficult specimens.
However, it may still be necessary to send difficult specimens to an expert
with familiarity in this group of insects. There are currently no revised keys
available to North American Agrilusor other Buprestidae that include the
EAB.
An example of a species comparison to EAB
as used in this guide
Agrilus bilineatus(Weber) “two-lined chestnut borer”
• Length: 4.2-9.5 mm, slightly smaller than EAB.
• Distinctively colored bronze-black with white-
yellow pubescent stripes extending from
edges of pronotum backwards along length of
elytra
(only visible on dry specimens).
• Abdominal dorsum black in color
(red in EAB)
,
pygidium with carina and projecting spine
(similar to EAB)
.
• Hosts: oaks, chestnut, American hornbeam,
beech, and eastern hop hornbeam.
1. Scientific and common name
(if available) of the species
being compared to EAB.
2. Side-by-side comparison of
the species to EAB at the
same size scale.
3. Text box listing size range,
description of color and shape,
similarities and differences to
EAB, and known host plants.
4. Side, top and oblique views of
the species showing color and
shape characteristics.
5. Photos of the most diagnostic
characteristics that will aid in
separation of the species from
EAB.
6. Range map of the species.
12
6
54 3 bilineatuswith
carina/spine dorsum
of abdomen blackEAB with
carina/spine dorsum
of abdomen red Source of morphological characteristics, host records and
distributional data primarily from Bright 1987, Downie & Arnett
1996, and Fisher 1928.
Family:
Buprestidae
“metallic wood-boring beetles”
The genus Agrilusis one of 53 genera of Buprestidae found in North America.
Fortunately, species in the genus Agrilushave a very distinctive shape that will
easily separate them from most of the other common genera of Buprestidae.
Agrilusin general are more linear and cylindrical than other genera of Buprestidae
and the base of the prothorax is produced backward as a lobe, which is lacking or
less obvious in most other genera
(except Brachysand Chrysobothris)
.
Agrilus(EAB)
Anthaxia
Cypriacis
Pronotum in Agrilus
produced backward as
lobe
Agrilusare more
elongate and cylindrical
than other Buprestidae Note: specimens
are not all to the
same size scale
Acmaeodera Brachys Buprestis Chalcophora Chrysobothris
Dicerca
Melanophila/
Phaenops
Chrysophana
Identification of the
Emerald Ash Borer
Agrilus planipennisFairmaire
“emerald ash borer” (EAB) • Typical specimens are a bright, metallic, emerald
green color overall, with the elytra usually
appearing somewhat duller and slightly darker
green. The overall greenish coloration may also have
variable amounts of brassy, coppery or reddish
reflections, especially on the pronotum and ventral
surfaces.
• A few rare specimens of EAB are entirely coppery-
red, entirely bluish-green, or green with bluish elytra.
• Length:
• EAB in general is
somewhat larger in size
and more brightly metallic
green than most other
U.S. Agrilusspecies.
dorsal view ventral view
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