Confusing Blue Butterfly – a Cautionary Tale

Another beautiful sunny day butterfly put in an appearance and for once opened its wings briefly so that I could get good views of both upper and lower surfaces. Actual identification was not easy … to be honest I initially had it down as a Northern Blue Butterfly (Lycaeides argyrognomon) until I checked their range and found they are a western species … so I thought again and read some more and and decided that with their being nothing else like it then it was probably the very similar Orange-bordered Blue Butterfly (Lycaeides melissa). Thinking “that’s a lovely thing either way” I put the photos on this page and moved on to other matters.

But something nagged and I got in touch with Rick Cavasin who has published wonderful guides to the butterflies of Ontario and Quebec … and he put me right. This is what he wrote, and the story is fascinating:

The Melissa Blue ( Lycaeides melissa ) is a western species, except for the very rare eastern subspecies L. melissa samuelis or “Karner Blue”, which has been extirpated from Canada but still persists in a few isolated colonies in the Eastern US.   The Northern Blue ( Lycaeides idas ) is, as the name suggests, a Northern Species.  You would have to go  further North to find that one ( I’ve seen them out in Gaspesie, and in the Laurentians North of Quebec city ).
What you have there is probably the European Common Blue ( Polyommattus icarus ), which is shown on my website here:
As stated on the website, this species appears to have been introduced ( from Europe ) somewhere near Mirabel airport, and it has spread rapidly.   It is extremely common around Montreal, and I believe it has crossed over the river Eastward.   It will likely continue to spread since the larval host is Birdsfoot Trefoil ( Lotus corniculatus ) , a common ( introduced ) weed. The European Common Blue is slightly larger than our native Melissa/Karner and Northern Blues.   I can’t judge the size of your butterfly from the photos, but it is known to be common around Montreal.  It has around 3 flights per season, and should be on the wing right now.

So the pictures below are of the European Common Blue (Polyommatus icarus) 

** Rick Cavasin’s website is here – pay a visit:  http://www.quebec.butterflyguide.ca 20160903-20160903-001-2 20160903-20160903-002-2

Wikipedia says: Recently, the common blue butterfly was discovered in Mirabel, Quebec, Canada by Ara Sarafian, an amateur entomologist who observed the butterfly from 2005 to 2008. He contacted the Canadian National Collection of Insects in Ottawa where the butterfly was identified as Polyommatus icarus, a new alien butterfly to Canada and to North America. The butterfly seems to be well established and is extending its range from year to year.

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