Friday, June 1, 2012

How to know a fly: Mozzies & Midges

Male midge: plumose antennae, no beak
For the last few weeks the woods near lakes and rivers have been humming with midges. In spots where they swarm in numbers, the noise can be loud enough to cause comment and the size of the swarms may cause dread in those who confuse them with mosquitoes.
Male mosquito: plumose antenna + beak
Fortunately, midges (Chironomidae) do no harm and are integral parts of aquatic ecosystems. Like mosquitoes (Culicidae), male midges have plumose antennae used to follow a female's hum, but they lack the long beaks in between that define mosquitoes. Not that anyone need worry about being bitten by a male mosquito - they use their beaks to feed at flowers and do not take blood.
Female Ochlerotatus spencerii - arrow points to proboscis, stylets inserted
In the Edmonton area, we mostly have two types of mosquitoes. Species of Culex, Culiseta, and Anopheles overwinter as adult females and start biting in the spring. I sometimes see one in my backyard in the spring, but rarely. Usually they don't start showing up until later in the year. I think this is because they breed in lakes and marshes and it is a long way from the HBG to the closest lake. Around Elk Island, though, some of the very large and rather scary Culiseta have been landing and trying to bite the last two weeks. Fortunately, they have been few, rather clumsy, and mostly ended up as splats.
Female Aedes vexans - our most annoying puddle mozzie
The second type of mosquito is the snow melt/ flood water breeders in the genera Aedes and Ochlerotatus.  These overwinter as eggs laid in wet soil next to puddles of water from melting snow and heavy rains. The eggs need to be flooded to hatch. I keep track of when the first of these start biting in the Home Bug Garden and this year it was 14 May - intermediate between 8 May (2005) and 22 May (2009) - another indication that this is a moderate Spring. The other good news is that only one mozzie has shown up so far.
Male mozzie waiting for flower to open or female to fly by
After last year's horror mosquito summer, it seems a blessing, but a bit strange, that there have been so few snow melt mozzies. Perhaps the City's mosquito abatement program is working very well this year. Alternatively, the small spring snowpack and relatively dry May may mean that last year's eggs are sitting high and dry around the rims of last year's much larger puddles. I suppose that if we get heavy rains this summer, we will find out, but that is one hypothesis I'd rather not test. Especially, since there is another kind of mosquito, Culex tarsalis, that breeds in grassy puddles in the summer and transmits the West Nile Virus.


  1. Well, this was SUPER useful, thank you!

    The 1st photo, a non-mosquito, looked more mosquito-y than the 2nd photo, which actually was a mosquito. And I call myself a biologist?!?

    Thank you for the beak clue. =)

    I like that vexans is the species name of your most vexing mosquito. =) Delightfully apt.

  2. wow, I just noticed my blog is listed (1,000 thanks!!!) as the sole chicken blog. =) Hee.

    So, thought I should update you: They got wade pools today 'cause it's so hot. Probably time (hours later) to plop some ice cubes in their water tower AND wading pools. 'Course, they tend to snatch the cubes out of their wading pool, so it may be for naught. Regardless, it'll help take their mind of 90+ degree heat, poor girls. =)