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Luminous impressions of nocturnal pollinator research

By Paul Manning, B.Sc. student at Nova Scotia Agricultural College
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As an undergraduate student, I’ve been working diligently on the final hurrah of my four year career; the undergraduate thesis. I’ve been fortunate to work under the supervision of Dr. Chris Cutler for the past two summers, learning about the ecology and roles of insects within wild blueberry production. Though I’ve worked on a wide variety of projects within the lab, I’ve realized quickly that pollination was the aspect of entomology that I found to be particularly intriguing.

Blossoms of wild blueberry May, 23rd, 2012 (Photo by P. Manning)

One of the projects that caught my eye was as a continuation of a trial that our lab did in the summer of 2011. By sanctioning off areas of wild blueberries with cages that prevented pollinators from accessing the flowers, the team discovered that approximately a third of pollination events may be attributed to nocturnal insect activity, as well as weight of ripe berries being insignificant between nocturnal, and diurnal pollinated treatments.  Though a number of insects were collected using Malaise traps in this study, it was not possible to conclude captured insects were responsible for vectoring the pollen.

Lo and behold, there was a great opportunity for my thesis; to discover the identities of nocturnal pollinators within wild blueberry production. Armed with a sweep net, kill jars, a mercury-vapour lamp, tissue and enough ethyl-acetate to open my own nail salon we began to hit the field. Our sampling periods happened at two different times during the night; an early shift that started as soon as the sun went down, and a shift that started at 12:00 AM. Each sampling session lasted for two hours in length.

We implemented an interesting capture method, which worked extremely effectively. Under the glow of the mercury-vapor lamp, we placed a large 8×4 plywood board against the fence, making an 80° angle with the ground. When the insect landed upon the board, a quick capture could be made by placing the kill-jar against the board, and giving the board a small tap. This caused the insect to fly up into the kill-jar.

Screen illuminated by the mercury-vapour lamp (Photo by P. Manning)

June beetle captured with light trapping (Photo by P. Manning)

As the mercury vapor lamp began to buzz, insects began to make their way out of the dark and against our screen. The diversity was stunningly interesting, quite surprising. Tiny midges, large scarab beetles, hawk moths, and nocturnal icheumonids were included amongst our varied group of visitors.

Sweep samples were also taken in an area of darkness within the field. We used ethyl-acetate fumigated from a ventilated jar, within a larger Tupperware container to effectively kill the insects without struggle. The diversity from these samples was very different; being attributed mostly to beetles and small flies.

Insects were analyzed to find whether or not they carried pollen using methods. By swabbing the eyes, head, and mouthparts with a small cube of fuchsin gel.  By sealing these slides with the aid of a Bunsen burner, blueberry pollen was easily detected through its distinctive tetrad shape using a light microscope.

As the samples have been analyzed, the diversity of insects that may represent the nocturnal pollinators of wild blueberry is staggering. Though the work has been challenging and sometimes very tedious (have you ever attempted removing pollen off the head of a thrips?). I’ve learned a great diversity of things, including: an incredibly simple way to differentiate between icheumonids and brachonids; that there are an incredible number of fly families that vaguely-resemble a typical housefly; and that iced-cappuccinos do contain caffeine (after finally drifting off to sleep at 4:30 AM on a Sunday morning).

A small moth visits the light screen after sampling finishes (Photo by P. Manning)

This project has been a great way to open my eyes to the diversity of insects responsible for ecological functions. When prompted with the cue ‘pollination’ – my mind has been switched over from the typical image of a honey-bee – to a myriad of insect visitors among flowers. This is a vision of pollination which to me is something more; diverse, representative, and inclusive of this invaluable ecological service.

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References:

Beattie, A. J. 1971. A technique for the study of insect-borne pollen. Pan-Pacific Entomologist 47:82.
Cutler, C. G., Reeh, K. W., Sproule, J. M., & Ramanaidu, K. (July 01, 2012). Berry unexpected: Nocturnal pollination of lowbush blueberry. Canadian Journal of Plant Science, 92, 4, 707-711.

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About Crystal Ernst

PhD candidate (entomology) at McGill University working on beetle assemblages in Arctic Canada.

2 comments on “Luminous impressions of nocturnal pollinator research

  1. Question: Did you isolate the individual catches to keep them from contaminating other insects in the samples?

  2. We took as many precautions as possible to keep the insects from contaminating one another. The first was using high concentrations of ethyl acetate, which stopped most insects from struggling almost immediately.

    We tried to minimize contamination, through adding kim-wipes to isolate each insect after death. We also minimized the effects of contamination by waiting for the previous insect to die before capturing the next. The jars were cleaned out between each sampling session.

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