Macro Monday: Pine Tussock Moth Caterpillar

As a method of encouraging myself to blog more regularly, I bring to you Macro Monday. I’ll use this space to share images of interesting critters that, over the years, have been foolish enough to subject themselves to the Great Eye. The first subject for Macro Monday is a Pine Tussock Moth Caterpillar.

Dasychira grisefacta, lateral view. (I believe the head is on the right!)

I found this caterpillar trundling along the sidewalk at Athabasca Falls in Jasper National Park on 17 May, 2016. Noticing all the tufts and hairs, and recalling vaguely the defensive attributes of some caterpillar hairs, I immediately thought, “I bet that’s irritating!”.

Wanting to get a better look, and perhaps some photographs, I dropped to my knees and, with a soft brush, gently guided it into a plastic vial and took it to the nearest picnic table for a closer look. I had no clue what its natural food plant was, so I took photos of it on a plain white background.

I released it soon after, placing it on a log where it was immediately noticed by an ant, which, ignoring the obvious defences and overwhelming size difference, moved into attack.

I noticed that the hyperactive ant had a hard time getting past the various hair-tufts to get a grip on the caterpillar. Unfortunately, my photographic observations were cut short by protests from Wife, who noted that the caterpillar had no choice in the matter and that I was interfering with nature. The desire for marital harmony persevered over scientific discovery, so I rescued the caterpillar, photographed it again on white, and then placed it on a nearby (and ant-less) fir-tree branch, which satisfied She-who-must-be-obeyed.

Dasychira grisefacta, dorsal view.

I later found out that this was a Pine Tussock Moth (Dasychira grisefacta , Sub-family Lymantriidae) caterpillar. They are conifer specialists, taking particular delight in eating fir (Pseudotsuga sp.) needles, but also partaking in pine (Pinus sp.), western hemlock (Tsuga heterophylla) and spruce (Picea sp.). They are normally rarely seen, but there are occasional outbreaks that can completely defoliate trees. Their range covers most of western North America, from BC/Alberta south to New Mexico. The adults (right, from Wikipedia) are somewhat lacklustre in comparison to the larvae.

In hindsight, I wish I had spent more time photographing the caterpillar at higher magnifications to get more details of the various hair tufts. I am also left wondering just how effective the tufts and hairs are for deterring predators and parasites. If anyone knows of any literature about these details, please let me know.

(Thanks to Dave Holden of the Alberta Lepidopterists’ Guild for the ID.)


Forestry Service, USDA (pdf)

Pacific Northwest Moths

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