Plectrodera
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The cottonwood borer (''Plectrodera scalator'') is a species of
longhorn beetle The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described. Most species are characterized by Antenn ...
found in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
east of the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
that feeds on cottonwood trees. It is one of the largest insects in North America, with lengths reaching and widths, . It is the only species in the genus ''Plectrodera''.


Description

The adult cottonwood borer is a large
longhorn beetle The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described. Most species are characterized by Antenn ...
with a black-and-white coloration and black antennae as long or longer than the body."Cottonwood Borer." Texas A&M. http://insects.tamu.edu/fieldguide/bimg177.html Retrieved 2012-02-24. The white portions are due to microscopic masses of hair."Cottonwood Borer." Great Plains Nature Center. https://gpnc.org/fauna/insects/cottonwood-borer/ Retrieved 2025-07-16. The
larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...
have legless, cylindrical, creamy-white bodies with a brown-to-black head and grow up to long.


Life cycle

The female cottonwood borer will chew small pits in the base of the tree in which to lay her eggs. The larvae can take up to two years to mature, after which they
pupate A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages the ...
in a root below ground level for approximately three weeks. Once
metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...
has completed, the now-adult chews its way out of the root and digs up to the surface.


Environmental impact

Although larvae can kill young trees by
girdling Girdling, also called ring-barking, is the circumferential removal or injury of the bark (consisting of cork cambium or "phellogen", phloem, cambium and sometimes also the xylem) of a branch or trunk of a woody plant. Girdling prevents th ...
them, infested mature trees are usually not seriously injured. The larvae can also structurally weaken a young tree, which is then more susceptible to falling over in high winds. Adults feed on leaf stems and the bark of tender shoots, occasionally causing flagging.


References

{{taxonbar, from1=Q15872244, from2=Q5175849 Lamiini Beetles of North America Beetles described in 1792