Assisting with community inquiries is one of my favorite parts about being an entomologist. It’s nice to be able to help someone, and inevitably, I end up learning something new! This week, thanks to a call from Toledo, OR – I learned about the Pandora Moth (Hemileucinae: Coloradia pandora). True, this doesn’t classify as a ‘cutworm’, but I needed a place to post about it, so here we are. These large beauties have an unusual lifecycle, can be massive defoliators of pine trees in the Western US, and are used as a food source by Indigenous Peoples. Click the “Continue reading” link below if your curiosity is as strong as mine!

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A few months ago, a paper was published, confirming that Bogong moths (Agrotis infusa) use geomagnetic fields as a navigational tool for their en-masse aestivation flight.

Say what, now?

Long-range migrations are common in the insect world, the most ‘notable’ (as in..the one in which most people take an interest) is that of the monarch butterfly. The migrations occur each year, are purposeful, and serve some ecological function; to reach breeding sites, etc..

In the case of the Bogong moth, millions of moths leave the plains of Australia and fly towards the high country of the Victorian alps to escape the heat and avoid desiccation. They congregate in such large numbers in the mountainous habitat that indigenous peoples would go there to collect the moths as a food source. They are also a preferred staple for mountain pygmy possums. In autumn, the moths return to the plains to lay eggs and the cycle begins again.

Aestivation is just a fancy word for: reduced state of biological activity that occurs in response to hot and dry conditions. It is a sort of ‘summer hibernation’, if you will.

Closer to home, we have Euxoa auxiliaris that exhibits the same pattern (replace pygmy possums with grizzly bears and Australian Alps with Rocky Mountains). The study found that successful orientation relies on a combination of visual cues and magnetic frequencies emitted by the earth, and that when either cue was missing or altered, their flights became uncoordinated and erratic.

Many other creatures exhibit magnetoreception (using geomagnetic signals to navigate): migratory songbirds, salmon, sea turtles, and others. 2021 update: leaf-cutter ants

Now we just someone to develop the superhero series for these Persistent, Amazing, Perceptive, and Strong …mutants?

No, wait – that name’s already taken:

Photo (C) Merrill Peterson, PNW Moths


Author note: not sure why the Dreyer et al. is being referred to as the ‘first’ discovery – 1. Baker, R.R. and J.G. Mather, Magnetic compass sense in the large yellow underwing moth, Noctua pronuba L. Animal Behaviour, 1982. 30(2): p. 543-548.

Other note: concerns of pesticide distribution, bioaccumulation and toxicity levels in this type of system have been raised since at least 2006, and warrant further review, IMO

Apamea moths are flying now. Larvae are cutworm pests of grasses.

Apamea cutworms can be serious pests of grasses. There are a few different species that are common in this region. Two of them have fun common names.

A. cogitata, the thoughtful Apamea

and its more unfortunate contrary:

A. dubitans, the doubtful Apamea

The current activity of this common group of moths is not of direct concern. Rather, it is the active, overwintering larvae that are considered pests because they feed on grass roots.  A. dubitans and A. cogitata could be similar to the congeneric A. devastator, which only has 1 generation per year. I made a post about them in February.

In western Oregon, glassy cutworm (Apamea devastator) moths emerge in late June, peak in July, and larvae take 100-120 days to develop, depending on daylength1. The species we caught in traps this week (thoughtful and doubtful) are less well-studied. But I wager a guess that we could begin to see larvae in fields by about mid-September.

Fun fact: “cogitare” translates from Latin as “to think”. One of Francis Bacon’s most famous works “Cogitata et visa” (“Thoughts and Conclusions”) was written in 1612. In it, he posed that philosophy and science have common interests.

 1 Kamm, 1990. Biological observations of glassy cutworm in western Oregon. Pan-Pac.Ent. vol. 66