Observation of the week – June 12-18, 2021

Before I tell you about our sixth OOTW, I would like to say a big THANK YOU to all of you for helping us record over 500 observations of 39 butterfly species! This puts us well on track for having our best Butterfly Blitz yet. I can’t wait to see how many observations and species we have achieved by the end of the season!

And now onto our OOTW, which is a butterfly that I am thrilled to be able to tell you about – the Harvester. This Harvester was seen by participants Michelle (@michlocke) and Andrew (@uofgtwitcher) at the end of a long day of butterflying at Jack Darling Memorial Park and Rattray Marsh.

I am excited about this OOTW because it is our first record for this species for the Butterfly Blitz, it is a beautiful photo, and because the Harvester has a very interesting life cycle – it is North America’s only carnivorous butterfly.

Adult Harvester butterflies lay their eggs in woolly aphid colonies, and the caterpillars grow up snacking on the aphids all around them. Adults are also odd eaters; they feed on aphid honeydew (a sweet liquid produced by aphids as they feed), dead animals, animal dung, and mud. Their proboscis (i.e., tongue) is specialized for these foods and is too short to reach the nectar of most flowers.

Aphids do not move around much and hang out in large groups, so you’d think they would be an easy feast for predators. But aphid colonies are usually protected by ants, which herd and defend them in exchange for honeydew. Harvester caterpillars avoid being found out by these bodyguards by covering themselves in aphid wax and body parts, making themselves look and even smell like aphids to the ants. There is also evidence that they make sounds and vibrations that mimic those made by aphids. In the end, the ants end up protecting the Harvester caterpillars too – even though they are eating their aphid herd!

One thing I like about the OOTW photo is that you can see strands of what looks like aphid wax (the ‘wool’ from the woolly aphids’ name) stuck to the butterfly’s wings. You can imagine that it was recently in among a colony of aphids, laying eggs.

Harvester populations are closely to tied to woolly aphid populations, and they may come and go at a particular location with the aphid populations there. One of their most common food sources are Woolly Alder Aphids , and so Harvesters are often found in shrubby wet areas where alders grow.

This is exactly where Andrew and Michelle spotted their Harvester at Rattray Marsh. Andrew says: “I had paused to look at my phone when I noticed a small shadow flitting above me. After a frantic few seconds of trying to find the culprit, I was quite certain I had a Harvester butterfly by the size, shape and flight style of this little gem. I also realized I was standing next to a patch of alder […]. Eventually the butterfly landed perfectly in view on top of a leaf.

Rattray Marsh may be home to a long-standing population of Harvesters, as it is the only spot in the Credit River Watershed where they have been observed in the past 18 years. Although this is a busy park, Andrew says: “Amazingly this sighting took place immediately beside the waterfront trail (a paved path) and within meters of an extremely busy park with bikers, walkers, picnickers and beach-goers.

Its also likely that there are other Harvester populations in the watershed that have not been noticed before. Their high protein diet means that Harvester caterpillars develop very quickly compared to other butterfly species, going from egg to pupa in just over a week. And adult Harvesters are fast and unpredictable fliers. To see a Harvester, you need to be in the right place at the right time – which takes knowing something about their biology and also a bit of luck.

Have you had any lucky butterfly finds this year? Let us know in the comments – we’d love to hear about it!

Anotado por lltimms lltimms, 22 de junio de 2021 a las 06:53 PM

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