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Anthonomus grandis

By Ben Thompson

Geographic Range

Central America, Mexico, Cuba, and across the southern United States, throughout the regions where cotton is cultivated. It was introduced into the U.S. from Mexico in the late 1800's (Milne and Milne 1980).

Habitat

The boll weevil lives in and around areas where cotton is cultivated. In the spring, it mates and develops inside the cotton plant. It spends the winter in trash and leaf liter in the surrounding area (Drees and Jackman 1998).

Physical Description

Adult boll weevils are small (4-7 mm) beetles, and are covered by small, hairlike scales. The have a long beak or snout that extends about half the length of the body. Their color varies with age and sex from, but is basically brown, ranging from yellowish, reddish, grayish, to very dark brown. They have a distinctive double-toothed spur on the inside of each front leg. The larval stage is a white grub. The grub transforms into a brownish pupa that somewhat resembles an adult. (Milne and Milne 1980, Drees and Jackman 1998)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • Range length
    4 to 7 mm
    0.16 to 0.28 in

Development

Once eggs are laid the larvae hatch in about 5 days and spend the next 1 to 2 weeks feeding before developing into pupae. After pupating for about a week, adults emerge from the boll in which they developed by chewing their way out. Boll weevils can mature from egg to adult in less than 20 days, and as many as seven generations can mature in one year (Drees and Jackman 1998). (Drees and Jackman, 1998)

Reproduction

In the spring, adult boll weevils fly to cotton fields and feed for three to seven days. The weevils then mate, and the females bore into the flowers and bolls of the cotton plant and lay their eggs. (Drees and Jackman, 1998)

  • Breeding interval
    As many as seven generations of boll weevils can occur in a year.
  • Breeding season
    Breeding occurs during the warm months of the year.
  • Range age at sexual or reproductive maturity (female)
    20 (low) days
  • Range age at sexual or reproductive maturity (male)
    20 (low) days

Once the eggs are laid in a boll there is no further parental care.

  • Parental Investment
  • no parental involvement

Food Habits

The boll weevil lives and feeds only in cotton and closely related plants. They eat the seed pods (bolls) and the buds of the cotton flower (Milne and Milne 1980).

  • Plant Foods
  • seeds, grains, and nuts

Economic Importance for Humans: Negative

The boll weevil can destroy entire cotton crops. When the bolls are infested with weevils, they turn yellow and fall off the plant, ruining the cotton fibers. If cotton is heavily infested, the plants may still grow, but produce few bolls, which are the parts of the plant which produce the cotton fibers which we use. (Drees and Jackman 1998)

The boll weevil is an infamous pest, that has been "the bane of cotton farmers throughout the United States" since it was accidentally introduced from Mexico in the 1800's (Milne and Milne 1980).

Until recently control of the Boll Weevil on U.S. cotton crops frequently required heavy use of chemical pesticides. This situation is changing, but in some areas, commercial cotton farming still use substantial quantities of dangerous pesticides.

The United States Department of Agriculture's Animal and Plant Health Inspection Service is sponsoring a Boll Weevil eradication program that has eliminated the species from several states (USDA APHIS 2001)

  • Negative Impacts
  • crop pest

Conservation Status

Other Comments

There is a Boll Weevil Monument in the city of Enterprise, Alabama. It was built in 1919 to commemorate the economic diversification that was required after boll weevils devastated cotton crops, the only local product. (Encyclopædia Britannica Online 2001, Thom 1996)

Contributors

Ben Thompson (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Arnett, R. 1985. American Insects. New York: Van Nostrand Reinhold Company.

Drees, B., J. Jackman. 1998. A Field Guide to Common Texas Insects. Houston: Gulf Publishing Company.

Encyclopædia Britannica Online, 2000. "Enterprise" (On-line). Accessed March 05, 2001 at http://www.eb.com:180/bol/topic?eu=1475&sctn=1.

Milne, L. 1980. The Audobon Society Field Guide to North American Insects and Spiders. New York: Alfred A. Knopf.

O'Toole, C. 1986. The Encyclopedia of Insects. New York: Facts on File Publications.

Stoetzel, M. 1989. Common Names of Insects and Related Organisms. Entomological Society of America.

Thom, C. 1996. "Boll Weevil Monument" (On-line). Accessed 12 March 2001 at http://www.thom.org/gallery/statues/weevil/.

USDA APHIS, 2000?. "Boll Weevil Eradication" (On-line). Accessed 12 March 2001 at http://www.aphis.usda.gov/ppq/weevil/.

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