Category Archives: Cerambycidae

Megasemum asperum, a Cerambycid Beetle

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Megasemum asperum, a Cerambycid Beetle

Here is a new-to-me Cerambycid (longhorn) beetle. I haven’t added one of these to my photo collection in the 15 years I’ve lived on San Juan Island, so note here that they are “UNCOMMON” and not populous in number.

This species is the only one in its genus in North America. It is Megasemum asperum. I see in perusing iNaturalist.org that there have been 67 reported observations dating back to 2007.

Location: San Juan Island, WA

ID: Megasemum asperum

From Bugguide.net –

Size: 18-25mm

Season: July to August (this is when you could see an adult)

Numbers: a single species in the New World & in NE Asia

It was described by John Lawrence LeConte in 1854

From Beetles of Western North America – “Larvae mine Douglas-fir (Pseudotsuga menziesii) and fir (Abies). Adults are attracted to lights during the summer. Found in coniferous forests of western North America,” (Dr. Art Evans, entomologist, 2021).

Your take away message – NOT a pest. NOT a tree killer. NATIVE species! Performs important recycling of nutrients role in ecosystems allowing regeneration in our forests. Appreciate Biodiversity.

Thanks for reading!

Monochamus scutellatus, the Whitespotted Sawyer Beetle

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Monochamus scutellatus Canoe Island August 12, 2019 Photo by Chase Stoddard
Monochamus scutellatus
Canoe Island, August 12, 2019

I received this photo yesterday of a very cool Cerambycid (Long-horned) beetle from Chase S. on Canoe Island, WA. This is a Whitespotted Sawyer beetle (Monochamus scutellatus). These beetles are found in forested areas across the continent. The first time I saw one on San Juan Island, I almost mistook it for a giant black spider. Its long antennae give it the appearance of having eight legs, like an arachnid.

The larvae (known as sawyers) of Monochamus beetles develop in the wood of fire-scorched, diseased or injured, dying pine, Douglas fir, true firs, and spruce trees. The adult beetles lay eggs in slits in tree bark. Larvae (grubs) develop through several instars before pupating. The younger larvae feed on wood beneath the bark and filling the void with long, fibrous borings, then move into the wood, forming holes that will become almost perfectly round as the tunnel grows deeper. The tunnels can eventually reach the heartwood of the tree.

Prior to pupation, the larvae will pack the deep gallery with grass, leaving a space at the end for the pupal cell or chamber. Adults will emerge by gnawing through the cell and a thin layer of wood and bark to the surface. Telltale signs of boring damage is the accumulation of debris along infested logs. As they can attack and damage recently felled trees, they are considered a pest in logging areas. According to Furniss and Caroline’s 1977 Department of Agriculture Forest Service Publication No. 1339, utilization of preventative methods that avoid leaving logs exposed during the beetles’ egg laying period ( July-September ) is the best approach.

Monochamus scutellatus White-spotted Sawyer
August 30, 2010
Photo by Cynthia Brast
San Juan Island, WA

References:

Furniss, R. L. (Robert Livingston)., Carolin, V. M. (Valentine M.)., United States. Forest Service. (1977). Western forest insects. [Washington]: Dept. of Agriculture, Forest Service : for sale by the Supt. of Docs., U.S. Govt. Print. Off..

Haggard, P. and Haggard, J. (2006). Insects of the Pacific Northwest. Timber Press Field Guide.

Peterson, M.A. (2018) Pacific Northwest Insects. Seattle Audubon Society.

Xestoleptura crassipes on Pearly Everlasting (Anaphalis margaritacea)

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Xestoleptura crassipes

Flower Long-horned Beetle (Xestoleptura crassipes) on Pearly Everlasting (Anaphalis margaritacea)