Eustenopus villosus
Encyclopedia
Eustenopus villosus is a species of true weevil
known as the yellow starthistle hairy weevil. It is used as an agent of biological pest control
against the noxious weed yellow starthistle (Centaurea solstitialis).
The adult weevil is hairy and brown with white stripes. It is 4 to 6 millimeters long, not including its long snout. The female chews a hole in a closed flower head
, deposits an egg inside, and seals the hole with a dark-colored mucilage
. This visible hole can warp the shape of the flower head as it grows. The larva
emerges from its egg in about three days and begins to feed on the flower parts and developing seeds. In just over two weeks the larva can destroy all or nearly all of the developing seeds. It uses the scraps to build a chamber in which it pupa
tes for one to two weeks and then leaves the flower head as an adult. Both larva and adult of this species contribute to the damage done to the plant. The larvae eat the seeds in mature flower buds and the adults feed on smaller buds, destroying many. This weevil will readily attack many invasive Centaurea species, but has not been known to damage native flora.
This weevil is native to southern Europe and the Mediterranean. It was first released as a biocontrol agent in the United States in 1990 and it is now established in much of the western United States wherever yellow starthistle grows. It is considered one of the more efficient yellow starthistle biocontrol agents.
Curculionidae
Curculionidae is the family of the "true" weevils . It was formerly recognized in 1998 as the largest of any animal family, with over 40,000 species described worldwide at that time...
known as the yellow starthistle hairy weevil. It is used as an agent of biological pest control
Biological pest control
Biological control of pests in agriculture is a method of controlling pests that relies on predation, parasitism, herbivory, or other natural mechanisms...
against the noxious weed yellow starthistle (Centaurea solstitialis).
The adult weevil is hairy and brown with white stripes. It is 4 to 6 millimeters long, not including its long snout. The female chews a hole in a closed flower head
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
, deposits an egg inside, and seals the hole with a dark-colored mucilage
Mucilage
Mucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
. This visible hole can warp the shape of the flower head as it grows. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
emerges from its egg in about three days and begins to feed on the flower parts and developing seeds. In just over two weeks the larva can destroy all or nearly all of the developing seeds. It uses the scraps to build a chamber in which it pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
tes for one to two weeks and then leaves the flower head as an adult. Both larva and adult of this species contribute to the damage done to the plant. The larvae eat the seeds in mature flower buds and the adults feed on smaller buds, destroying many. This weevil will readily attack many invasive Centaurea species, but has not been known to damage native flora.
This weevil is native to southern Europe and the Mediterranean. It was first released as a biocontrol agent in the United States in 1990 and it is now established in much of the western United States wherever yellow starthistle grows. It is considered one of the more efficient yellow starthistle biocontrol agents.