NC STATE UNIVERSITY
Identification of
Common Ground Beetles
in North Carolina Coastal Plain
Agricultural Fields
This publication provides an illustrated key to the major groups (or tribes: see definition in
next section) of ground beetles found in eastern North Carolina agricultural fields. Feeding
habits of beetles within the same tribe are often very similar, allowing rough separation of
beetles that are predators and seed feeders, for example. This document will allow accurate
identification of the vast majority of ground beetle collections made in this area. For a
comprehensive academic document describing all ground beetles in the region, see Ciegler
(2000), listed in the reference section at the end of this document.
Although there are thirty-six currently recognized tribes of carabid beetles, this publication focuses
on the nine that are most likely to be encountered in eastern North Carolina agricultural fields. The
tribes presented here are based on a survey of academic literature and monthly pitfall trap collections
of ground beetles taken in nine fields from July 2009 through July 2010 at the Center for Environmental Farming Systems near Goldsboro, North Carolina. The fields included a wide variety of soil
types supporting hay, soybeans, or corn. The majority of beetles collected (>95 percent) were of eight
species from five tribes: Carabini, Cicindelini, Harpalini, Pterostichini, Zabrini. Although specimens
from the tribes Chlaeniini, Galeritini, Platynini and Scaritini were not as abundant, they were collected consistently enough to warrant inclusion here. For those less familiar with insect classification
and where tribes fit into this system, see the brief description that follows.
Classification of Ground Beetles
The basic hierarchical naming system used in insect classification (taxomomy and systematics) is
presented below, with examples. A complete description of insect classification, and how insects relate
to other organisms, can be found at the online Tree of Life Project (www.tolweb.org).
Class (e.g. Insecta, the insects)
Order (e.g. Coleoptera, the beetles)
Family (e.g. Carabidae, the ground beetles)
Tribe (e.g. Cicindelini, the tiger beetles)
Genus (e.g. Megacephala, the big-headed tiger beetles)
Species (e.g. Megacephala carolina, the Pan-American big-headed tiger beetles)
This publication provides an identification tool set up as a dichotomous key, which is a logic tool
using characteristics of an organism arranged into pairs of statements (couplets) that allow you
to choose which statement fits the organism best. Once the choice is made, you will have identified the beetle or will be directed to following couplets until the organism is identified. Always
read both couplets and examine the pictures (figures) provided before making your decision. The
number in parentheses following the ”a” of each couplet (from couplet 2 on) is the number of the
previous couplet.
This key uses characteristics of beetles that are identifiable using a good hand lens. For a more
detailed taxonomic description of these features, see Ciegler (2000).
Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
1a With labrum (upper lip) clearly wider than gap between antennal insertions (i.e. very large mouthparts) (Fig.1A); mandibles long and with long teeth; elytra (the hardened forewing) without striations (grooves) (Fig. 2A) ........................................................CICINDELINI (Tiger beetles).
Feeding Habits: predatory on grounddwelling arthropods.
1b
Not as above; gap between antennal insertions wider than labrum (Fig. 1B); elytra with grooves
(Fig. 2B) ........................................................................................ Go to couplet 2.
Figure 1. Width of labrum vs. gap
between antennal insertions for:
A: Cicindelini (Photo by David Cappaert,
Michigan State University).
B: Harpalini.
Figure 2. Elytra and labrums compared
for: A: Cicindelini (Megacephala carolina) (Photo by Alexander V. Anichtchenko,
Carabidae of the World Project).
B: Harpalini (Harpalus pensylvanicus)
(Photo by Henri Goulet, Agriculture and
Agri-Food Canada).
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
2a (1) Body pedunculate, i.e. thorax constricted to a “waist” giving the overall appearance of a mole cricket
(Fig. 3); front legs flattened and modified for digging (Fig. 3, circle); large beetles 15- 30mm ( 0.6-1.2
inches) ...................................................................................... SCARITINI.
Feeding Habits: predatory/ omnivorous
on caterpillars, wireworms, other insects,
and occasional plant matter.
2b Not pedunculate; front legs not modified for digging ........Go to couplet 3.
3a (2) Head and pronotum (upper surface of the first segment of the thorax; it’s shape is often important
Figure 3. Scaritini (Scarites subterraneus). Circle showing fossorial (modified for digging) front legs. (Photo
by Henri Goulet, Agriculture & Agri-Food Canada)
in beetle identification) narrow, equal to or less than the width of one elytron (hard forewing of a
beetle); head narrows posterior to eyes with definite neck between head and prothorax; head and
elytra black, pronotum and legs red; larger beetles 17-22 mm ( 0.7-0.9 inches) .
(Fig. 4)............................................................................................ GALERITINI (False bombardier beetles).
Feeding Habits: predatory/omnivorous
on caterpillars and grass seeds.
3b Head and pronotum wider, or if head and pronotum narrow, not colored as above; without a defined
neck; smaller beetles <17mm (<0.7 inches) .........................Go to couplet 4.
Figure 4. Galeritini (Galerita sp.). Head and pronotum
equal to or a little less than the width of a single
elytron. (Photo by Henri Goulet, Agriculture and AgriFood Canada)
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
4A (3) With at least 11 clearly impressed and evenly spaced grooves (striae) on each elytron (the hard
forewing of a beetle); this character is most easily seen at the basal part of the elytron; i.e. closest to
head(Fig. 5A); often with colorful depressions (foveae) on black elytra; larger beetles, over 15mm (.6
inches), more often 20-25mm ( 0.8-1.0 inches) (Fig. 6) .....CARABINI (Fiery searchers
and caterpillar hunters).
Feeding Habits: predatory mainly on caterpillars often found on plants in agricultural settings.
4B With 8 striae (grooves) per elytron (Fig. 5B); may be variously colored;
various sizes .............................................................................Go to couplet 5.
Figure 5. A: Carabini
(Carabus vinctus) showing
dense striation.
B: Harpalini (Harpalus
caliginosis) with 8 complete
striae.
Figure 6. Carabini (Calosoma sayi) showing
elytral foveae (green dimples).
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
5a (4)
With 1 supra-orbital setigerous puncture (a pit with a hair above the eye; the hair may be lost, leaving only the pit) (Fig. 7A) ......................................................Go to couplet 6.
5b With 2 supra-orbital setigerous punctures (Fig. 7B) ..........Go to couplet 7.
Figure 7. Setigerous punctures
(pits with hairs). A: Harpalini with
single puncture above eye.
B: Pterostichini with two punctures above eye.
6a (5) With an interruption of the margin of the elytra (internal plica) near the apex where the lateral
edge is replaced by secondary vein (this is a difficult character to see and may require lifting an
elytron to better see the edge) (Fig. 8); with fine matt of velvet-like hair covering dorsum of elytra
(Fig. 9) .......................................................................................CHLAENIINI
Feeding Habits: predatory/omnivorous
mainly on arthropods and other invertebrates, but also fungi.
6b Without an interruption of the margin (internal plica) of the elytra near the apex (the lateral edge is not
replaced) (Fig. 8); elytra without matt of fine hair (Fig.9) ... HARPALINI
Feeding Habits: herbivorous/omnivorous
primarily on weed seeds but will also feed
on other arthropods if needed.
Figure 8. Underside of elytron that
was lifted to reveal: A: Elytral margin interruption (or internal plica).
B: Elytral margin uninterrupted.
Figure 9. Beetles with single supra- orbital setigerous punctures A: Chlaeniini (Chlaenius tricolor).
B: Harpalini (Harpalus pensylvanicus).
Photos by Henri Goulet , Agriculture AgriFood Canada.
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
7a (5)
With an interruption of the margin (internal plica) of the elytra near the apex (this is a difficult
character to see and may require lifting an elytron to better see the edge) (Fig. 10); with pronotum
considerably wider than one elytron (Fig. 11A)...................Go to couplet 8.
7b
Without an interruption of the margin (internal plica) of the elytra near the apex (Fig. 10); and with
pronotum about the width of one elytron (Fig.11B); not metallic
....................................................................................................PLATYNINI
Feeding Habits: predatory on caterpillars,
aphids, mealworms
Figure 10. A. Elytron lifted to
reveal elytral margin interruption
(or internal plica).
B. Elytral margin uninterrupted.
Figure 11. Pronotum and elytral
widths. A: Pterostichini (Poecilus
chalcites) (Photo by Henri Goulet,
Agriculture Agri-Food Canada).
B: Platynini (Agonum punctiforme).
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Key
8a (7)
Punctures on elytra; usually two setae (hairs) on the second segment of the labial palpi (inner fingerlike palps of the mouthparts); usually black but one dominant species (Poecilus chalcites) is metallic
bronze/green (Fig. 12) ............................................................PTEROSTICHINI.
Feeding Habits: predatory on arthropod
and other invertebrates, especially caterpillars and beetle eggs.
8b
No punctures on elytra; usually many setae on the second segment of the labial palpi (inner fingerlike palps of the mouthparts); oval shape, and dark bronze coloration, not metallic; commonly running about in the sun May-early June. ..................................ZABRINI (Amara is the only genus
located in NC).
Feeding Habits: omnivorous on plant
seeds, caterpillars.
Figure 12. Body shape and color.
A: Pterostichini (Poecilus chalcites)
(Photo by Henri Goulet, Agriculture
Agri-Food Canada).
B: Zabrini (Amara cupreolata).
Table 1. Summary of supra orbital setae and plica states for
relevant tribes.
1 supra orbital seta
2 supra orbital setae
Plica
Chlaeniini
Pterostichini/Zabrini
No plica
Harpalini
Platynini
References
Ciegler, J. C. 2000. Ground Beetles and Wrinkled Bark Beetles of
South Carolina (Coleoptera: Geadephaga: Carabidae and Rhysodidae). Biota of South Carolina Vol. 1. Clemson University, Clemson, S.C.
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Identification of Common Ground Beetles in North Carolina Coastal Plain Agricultural Fields
Prepared by
Geoff Balme, Department of Entomology, NC State University
David Orr, Department of Entomology, NC State University
Published by
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regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
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