White Spotted Pine Sawyer

 Highlighted Species:

White Spotted Pine Sawyer
Monochamus scutellatus

(Coleoptera: Cerambycidae)

Image 1: A whitespotted pine sawyer adult on a tree. (B.witty 2012).

About:

The white-spotted pine sawyer is a large, shiny, black and white speckled longhorned beetle ranging across the U.S. and Canada. Adults seek weakened or dead coniferous trees, largely the eastern white pine (Pinus strobus) but includes other species of pines, firs, and spruce. The process of the larva growing, developing, exiting from the tree helps the break-down of the tree material. The galleries and exit holes allow for wood-decaying fungi and other insects to enter quickly and begin their recycling habits.

Image 2: Nat's pine sawyer nails, posed against a dead pine snag (Naterpillar, 2024).

The white-spotted pine sawyers have a two-year life cycle. After mating, the female chews a slit in the bark and deposits a white, oblong egg. The tiny larva emerges and begins to burrow into the tree, where it will chew and move throughout the layers of the tree creating galleries. The large, flattish grub will grow bigger and burrow deeper into the trunk where it overwinters. After a winter rest, it continues to eat and grow to full size before creating a pupation chamber, where it will once again overwinter. As temperatures warm into late spring and summer, the adult beetle emerges and chews its way out of the bark, exiting from a nearly perfectly circular hole in the bark. The adults will feed nearby on shoots and leaves, mating in the summer and continuing the cycle when a new egg is laid in the pine log.

Image 3: Just as in nature, these pine sawyer nails are drawn to a dead pine: the pine is being broken down by algae, fungi, and bacteria, and insect galleries can be seen. (Naterpillar 2024).

In spring when adult white-spotted pine sawyers emerge, one might confuse their sighting with that of an Asian Longhorned Beetle (Anoplophora glabripennis). Both are large, conspicuous black and speckled longhorned beetles. Unlike the white-spotted pine sawyer, the Asian longhorned beetle (ALB) is an introduced species. Primarily seeking out maples, elms, birches, poplars, willows and several more species, the ALB will choose healthy living trees for oviposition rather than dead and weak trees. Because of this, the many generations of larva growing and developing in a tree will eventually weaken and kill the tree, making the ALB an environmentally and economically important insect. 

Image 4: It's all about that white scutellum. (Naterpillar 2024).

The best way to tell a pine sawyer apart from an Asian Longhorned beetle is the white spot on the upper middle part of the wings, called a scutellum. As the name suggests, the white spotted pine sawyer will have a large white dot where the wing coverings meet together at the top. The ALB will not have this dot, and thus is an easy tell. Additionally, some context clues such as what type of tree (deciduous, coniferous) may be helpful to determine where it came from. For more information about the Asian Longhorned Beetle, you can visit the USDA APHIS website for details.

Design Notes:

To represent the pine sawyer, I started with a dark brown base. Adding black and white polka dots for the speckled coloration, and finally a large white “scutellum” at the top of my nails.

Resources:

Animal and Plant Health Inspection Service. (24 July
2024). Asian Longhorned Beetle. U.S. Department of
Agriculture.
https://www.aphis.usda.gov/plant-pests-diseases/alb

B. Witty. (5 May 2012). Whitespotted Sawyer -
Monochamus scutellatus [Photograph]. BugGuide.
https://bugguide.net/node/view/1103714

Natural Resources Canada. (27 October 2011).
Whitespotted sawyer. NRCan.
https://tidcf.nrcan.gc.ca/en/insects/factsheet/900

Wilson, Louis F. (June 1975). White Spotted Sawyer.
Forest Pest Leaflet. U.S. Department of Agriculture
Forest Service.
https://www.fs.usda.gov/foresthealth/docs/fidls/FIDL-7
4-WhiteSpottedSawyer.pdf