A Good Pirate
The larger pirate bug could be a potent biocontrol in
A greedy pirate bug with an appetite for insects could help prevent damage
to stored grain products.
In nature's bug-eat-bug world, predators could help balance the ratio of
good bugs to bad.
The result could be smaller populations of all insects in stored products,
with less reliance on insecticides, says ARS entomologist Thomas W. Phillips,
formerly in the ARS Stored-Product Insects Research Unit at Madison, Wisconsin.
Although commonly called the larger pirate bug, Lycotcoris campestris
isn't very big. Only about an eighth of an inch long and dark brown in color,
it looks like a small stink bug or boxelder bug. However, the larger pirate bug
can tackle a caterpillar 10 to 50 times its size.
Phillips and Megha N. Parajulee, a University of Wisconsin graduate student,
were the first researchers to study the larger pirate bug as a potential
predator of stored-product insects. Now an entomologist with Texas A&M
University, Parajulee says the pirate bug in action "looks like a dog
attacking an elephant."
Among its favorite prey are the larvae of Indianmeal moths, which commonly
infest homes and commercial food warehouses. "They're responsible for
large expenditures by the multi-billion-dollar food industry for sanitation and
insecticidal treatments," says Phillips.
In addition to Indianmeal moths, L. campestris attacks and eats a
varied menu, including Mediterranean flour moths, almond moths, red flour
beetles, sawtooth grain beetles, and warehouse beetles.
"The pirate bugs are good guys, compared to the insect pests they
devour. They don't get inside grain kernels nor do they eat the grainonly
other insects. Their presence in warehouses and storage facilities represents
no threat to the quality of the grain. When it's processed, the pirate bugs can
be removed," says Phillips.
He and Parajulee began a 3-year study of the biology and behavior of the
pirate bugs in the summer of 1991. The researchers had been sampling corn from
Wisconsin farms when they found them in the samples. They began to see what the
bugs would do against a range of stored-product insects.
Using its needlelike mouth parts, the pirate bug injects a venomous saliva
that subdues its prey in less than a minute. Then the pirate bug sucks blood
and body juices from its victim.
Although hundreds of species of pirate bugs exist, this one is important
because it's found naturally in stored grain products. It's also been found
feeding on insects in manure, under the bark of dead trees, and in haystacks,
rotting leaves, matted-down grass, bird nests, poultry houses, and animal
In 1992 and 1993, the researchers studied the insect's behavior in a grain
storage facility on a farm near Madison. Populations of the predator survived
cold temperatures both on the farm and in laboratory studies.
Phillips says that "despite sub-freezing temperatures, live bugs that
were collected in the grain bin could feed on prey and reproduce as soon as
they warmed up."
Phillips and Parajulee developed a method to rear a colony of the larger
pirate bug in the laboratory. To study its food preferences, they paired it
with 27 stored-product insects and 3 non-stored-product insects.
All but two of these pests (the tobacco hornworm and the yellow mealworm)
died after meeting up with the pirate bug.
"The larger pirate bug is an ideal candidate as a biocontrol
agent," says Phillips. "There's no special diet to prepare for
rearing, so it could be easily adapted to commercial mass-production.
"Young pirate bugs are ready to feed on pests right after hatching.
They live about 100 days when feeding on prey and can survive up to 20 days
without food or water. That's important for a predator if it has to wait
between prey hatchings."
Phillips and Parajulee recently teamed up with James Throne, an ARS
entomologist formerly with the ARS Stored-Product Insects Research and
Development Laboratory in Savannah, Georgia. He is now at the U.S. Grain
Marketing Research Laboratory in Manhattan, Kansas. Together, they're
developing a computer model to predict how predator populations increase under
different environmental conditions. The model will help in planning strategies
for using the larger pirate bug for biological control of stored grain pests.
"We recognize that insect pests can't be entirely eliminated with
biological controls," says Phillips, "but by balancing the numbers of
predators and pests, we can keep pest numbers at lower levels." By
Linda Cooke, ARS.
"A Good Pirate" was published in the
March 1995 issue of
Agricultural Research magazine.