As you can tell, I was pretty excited to find this Mantidfly. In my experience they are a rarely seen insect, but very cool to see. Not only are they bizarre-looking and generally rare or uncommon, they've got a pretty cool life history as well. I didn't know much about them before so did some research and came across this excellent paper by Rob and Syd Cannings. All of the following information comes from this paper and should be credited to the authors, not me.
Like many insects, Mantidflies (Order: Neuroptera; Family: Mantispidae) are at the northern edge of their range in Canada with only four species in all of the country (all of which are found in Ontario). Only one species, Climaciella brunnea (the "Wasp Mantidfly"), is relatively widespread. The Wasp Mantidfly is, you guessed it, a wasp mimic and is the only species I had seen (twice) before in Ontario:
|Wasp Mantidfly at Deloro, Hastings on 15 June 2008|
|Wasp Mantidfly at Backus Woods, Norfolk on 3 July 2010|
The separation of those two species is done by the presence/absence of dark spots on the "wing tips and some crossveins of radial cells", which my specimen appears to lack. That puts the ID tentatively as Dicromantispa sayi. This is exciting because, according to the paper referenced above, this would be a (known) range extension for the species in Ontario, which, based on examined specimens, was restricted to the north shore of Lake Erie. I'm waiting to hear back from some folks who know more than I do to see if I can get that confirmed or find out more.
As I mentioned earlier, Mantidflies have a pretty cool life history. Their raptorial forearms give them away as predators as adults (feeding on a variety of other insects). As larvae, most develop in spider egg sacs where they feed busily on the individual spider eggs. In some species the larvae actively search out spider eggs sacs, but in others they board adult spiders and enter the egg sac during the construction phase. The eggs are stalked, similar to these Green Lacewing (Chrysopidae) eggs:
|Green Lacewing eggs at Heidelberg, Waterloo, 12 August 2005|
Cannings, R.A. and S.G. Cannings. 2006. The Mantispidae (Insecta: Neuroptera) of Canada, with notes on morphology, ecology, and distribution. Canadian Entomologist 138: 531-544.
Bug guide Mantidfly (Mantispidae) page
Update: I received confirmation from Rob Cannings that my identification was correct. Apparently there was also a record of this species near Tweed, Hastings County last summer, so it is probably worth looking for south of the shield in southeastern Ontario.