1. An insect hitchhiker: a plausible theory of migration of the bean
plataspid, Megacopta cribraria (Fabricius), throughout the
Southeastern U.S.
Brian M. McHouell, Brian A. Little, and Erika A. Scocco
Materials / Methods
Department of Biology, Wingate University, Wingate, NC 28174
Results
Introduction
Abstract
Conclusion
The preliminary results obtained show that M. Cribraria could theoretically utilize
car surfaces to aid in long distance traveling. This concept of travel seems more
plausible than that of random flight to kudzu patches due to kudzu’s use as an
anti-erosion preventative measure along roadways (Forseth, 2004). The idea of
“hitchhiking” could also provide a possible explanation to the rapid infestation of
the bean plataspid following their initial discovery in Oconee County, Georgia in
2009. Although initial results have shown support of the “hitchhiking” hypothesis,
further studies involving a larger specimen population, increased time limitations,
and varying wind speeds would be necessary to provide more accurate and long
Megacopta cribraria (Fabricius) is an invasive insect native to Southeast Asia, India, and Australia that was first detected in Oconee County, GA in 2009, which has since
spread into North Carolina, South Carolina, Virginia and Alabama. Host plants within its native range include a wide variety of legumes; however, kudzu, lablab, and
soybean are preferred by the insect. Researchers have theorized that the rapid infestation of the bean plataspid has been dispersed via weather patterns and/or by
attaching onto moving substrates (i.e., automobiles). Because of the close proximity of kudzu patches to roadways, the bean plataspid may have been able to disperse
abruptly. Because the bean plataspid has 2-segmented tarsi and setaceous tibiae, the latter suggesting that this insect can attach to substrates readily, the aim of this
study was to determine the possibility of the insect to attach to objects that are subjected to high wind disturbance to better understand if this is theory is plausible for
migration.
M. cribraria was initially detected in Oconee County, Georgia, in 2009. At that time only
9 counties in GA had reported an infestation of the insect, but by August 2011, the
insect had spread throughout Georgia, South Carolina, over half of North Carolina, and
parts of Virginia and Alabama (Fig. 1) (Zhang et al, 2012). During the fall months when
populations are highest, the plataspids will aggregate on light colored houses and cars,
which could be a means of insect spread (Eger et al., 2010). Thus, hexapods have
developed two distinctly different mechanisms in order to aid in surface attachment:
smooth pads or setose surfaces (Beutel et. al, 2000). M. cribraria utilize setose
covered tarsi and possess a tarsal claw located on the final tarsal segment, which
provides stability on surfaces (Fig. 2) (Gorb et. al., 2001). Knowledge of these
specialized appendages due to evolutionary adaptation and the described close
proximity of M. cribraria to vehicles have lead to the hypothesis that the dispersal and
rapid infestation of bean plataspids could be explained with the concept of traveling or
“hitchhiking” long distances with the aid of car surfaces. The aim of this study is test
the hypothesis of the “hitchhiking” bean plastaspid by determining whether the
specimen can stay attached to a surface when exposed to a wind current, and if so, the
length of time that they are able to maintain their attachment.
Insect Collection: M. cribraria were collected on kudzu in September 2011 and March 2012 from a
location in Wingate, North Carolina (GPS coordinates: 34o
59.644’N, 80o
29.171’W). Sweep nets were
used in a figure eight motion to capture the insects. They were then placed into rearing cages (25.4 cm 2
)
(Bioquip; Rancho Dominguez, CA) with soybean plants and transported back to the lab until needed.
Wind tunnel configuration: In order to simulate the transportation of bean plataspids on car surfaces, a
wind tunnel was engineered using a FlowPro®
utility blower (Selecture Inc.; Coppell, TX) and a single
0.61 m clear schedule 80 pipe (Excelon Thermo; Georgetown, DE) (Fig. 3). A platform was created by
using a 9.53 cm2
piece of plexi-glass (1 cm thick) that was placed in the center of the tube tacked with
beads of silicon. Six insects were placed on the platform with an average wind speed of 15 m/s. The
insects were then timed (seconds) until they were blown off the platform or for a maximum time limit of
900 s. Data was analyzed using the general linear model PROC GLM (SAS 9.2 2009) and Tukey HSD
test was used to compare insects. The average seconds will be used to calculate, theoretically, the
mileage that the insect could travel at the given wind speed. Calculation: 15 m/s = 34 mph (0.0094 mps
x 591 s = 5.6 miles)
2009 2010 2011
Megacopta cribraria Occurrence
Southern United States
2009-2011
Figure 1
(Courtesy of W.A. Gardner; UGA)
• The insects held onto the surface for an average of 591 s (p < 0.0009).
• There was variability in the amount of time that the insects could remain on
the platform (Table 1) (R2
= 0.48)
• Therefore, the insects could theoretically travel 5.6 miles before being
dislodged from the surface to which they were attached.
Insects Seconds*
1 200 c
2 369 bc
3 447 bc
4 684 ab
5 922 a
6 922 a
Figure 2
SEM of a tarsal claw.
Literature Cited
Beutel, R.G and S.N. Gorb. 2001. Ultrasound of attachment specializations of hexapods (Arthropoda):
evolutionary patterns from revised ordinal phylogeny. J. Zool. Syst. Evol. Research 39:177-207.
Eger, J.E., L.M. Ames, D.R. Suiter, T.M. Jenkins, D.A. Rider, and S.E. Halbert 2010. Occurrence of the Old World
bug Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae) in Georgia: a serious home invader and
potential legume pest. Insecta Mundi. 0121:1-11.
Forseth, I. and A. Innis. 2004. Kudzu (Pueraria montana): history, physiology, and ecology combine to make a
major
ecosystem threat. Critical Reviews in Plant Sciences 23:401-413.
Gorb, S.N. and R.G. Beutel. 2001. Evolution of locomotory attachment pads of hexapods. Naturwissenschaften
88:
530-534.
Zhang, Y., J.L. Hanula, and S.E. Halbert. 2012. The biology and preliminary host range of Megacopta cribraria
(Heteroptera: Plataspidae) and its impact on kudzu growth. Environmental Entomology. 41:40-50.
Figure 3
Wind tunnel configuration
Table 1. Statistical analysis for each insect tested using Tukey-Kramer LSD test.
* Means within columns followed by the same lower case letter are not significantly
different (Tukey-Kramer LSD, P<0.01)
SEM image of the tarsal claw and
setate.