Illinois Natural History Survey Reports

              A black and yellow beetle
emerges from the base of a
corn leaf and climbs up the
edge until it stops where the
leaf blade begins to bend
downward. It’s early July
in east-central Illinois and
the beetle, an male western
corn rootworm (WCR), is
feeding on corn pollen that
has accumulated at the base
of the leaf. As he rests, his
antennae alternately move up
and down, slowly sampling
the air for any drifting signals
from nearby females. After
many minutes, a whisp of
pheromone-laden air curls
around the male. His anten-nae
intercept the stream of sex
pheromone that signals a sexual-ly-
receptive female is somewhere
upwind. He pivots excitedly to
face into the oncoming stream of
intermittent pheromone mol-ecules.
In an instant, his wings
spread and he takes flight from
the edge of the leaf. After a short
period of slow, hovering upwind
flight, punctu-ated
by brief
detours in and
around several
plants, the rising
concentration of
pheromone tells
the male that the
female must be
near. He lands
on a plant a few
R e p o r t s
Summer 2006
No. 388
Inventorying the Pyre-nomycetes
of the Great
Smoky Mountains
National Park
2
Illinois’ Green
Infrastructure
3
Illinois Natural History
Survey Library Grand
Opening Celebration
4
Evaluating Streams
in Illinois Based on
Aquatic Biodiversity
5
Species Spotlight:
Assasin Bugs et al.
6
The Naturalist's
Apprentice: What's in a
Name?
7
In Memoriam: John
Bouseman
Insert
Continued on back page
INSIDE
Tracking Movement of Mate-seeking
WCR Males between Refuges and
Transgenic Corn
meters from where he began and
finds her clinging to the underside
of a leaf. He is the first male to
arrive. After a brief negotiation,
she accepts him and they mate.
When completed, they go their
separate ways; she will feed and
start to develop eggs, he feeds to
replenish his resources in prepara-tion
for another mating.
Movement is behavior at
its most fundamental. When
and where movement begins
and ends, who moves, and how
fast a mover goes all affect how
individuals are distributed in
populations. In WCR, like many
species, mate-finding involves
highly competitive males that
move in response to plumes of
sex-attractant pheromone they
use to locate unpredictably
distributed females that may only
be receptive to potential mates
for brief periods. Control actions
of pest managers that affect insect
distributions and/or the success
of mate-finding can influence pest
population dynamics.
Grower adoption of corn
rootworm-protected Bt trans-genic
corn hybrids (varieties that
express insecticidal toxins from
Bacillus thuringiensis (Bt) that
kill WCR larvae; adult WCR are
not harmed by Bt corn) protects
corn plants from economic injury
and changes the abundance and
distribution of WCR adults in
cornfields. To delay rapid devel-opment
of insect resistance to Bt
toxins, by law, growers using Bt
Pair of western corn rootworms (WCR) beetles mating on a corn leaf. Photo by
Joe Spencer, INHS Center for Ecological Entomology
Male WCR feeding in corn leaf collar. Photo
by Joe Spencer, INHS Center for Ecological Entomology