CADDISFLYS AROUND CHAMPAGNE

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July 28, 2020

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We have had several inquiries into what we plan to do about the Caddisflys and many of you have offered up suggestions.

Grounds Committee lead and Board member Dave Martin contacted the University of Calgary and had a prominent entomologist (John Swann) come and do an inspection of the property as well as the river. It's very interesting to note that he identified a new species and has stated that the health of our area of the Bow river is outstanding.

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Your Board has created an information deck on the Caddisfly and you can view it below. John has also provided some additional comments:

Nice to meet you this week. So I'm working my way through the material I collected and so far the adults that are flying around your complex at the moment are a species of Philopotamidae, Genus Dolophilodes probably the species c(Ling). Having just spent an hour looking at the male naughty bits of multiple specimens that's the species that I keep coming back to from multiple keying sources for every single specimen (to family and genus was easy)-- If you do a literature search on it you will find it's not recorded from AB -- known from BC, MT, ID, WY and other states as far south as California. Not surprising it's here but still a neat record. Interestingly, Philopotamidae are net-spinning caddisflies (as larvae) and have a low tolerance to pollution so the good thing is it says that your stretch of the river has good water quality based on the volume of those you are seeing.

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Moving onto the immatures I pulled out of the river.

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The really big stoneflies that were everywhere down there are in the family Perlidae-- Hesperoperla pacifica (Banks) and once again Hesperoperla has a very low tolerance to pollution.

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There were also lots of small Hydropsychidae caddisflies genus Hydropsyche -- there are 12 species known for AB. This is also a group of net-spinning caddisflies and have a low to moderate tolerance for pollution.

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I still have several more groups in the aquatic sample to id and the tiny caddisflies that were flying down around the river as well. I'll finish off the last few id's and try to brainstorm a few possible things that could help your complex's situation. Upshot is so far everything around you insect-wise says that the area of the river has very good water quality.

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Regards,

John

 

UPDATE AUGUST 6, 2020

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An update from John Swann.

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So to get back to your insect issue I’d like to start with the positives and the certainties. All the insects I collected around your complex were aquatic as immatures/larva and come out of the water (river) as adults to breed. The species/genera I collected and identified were all indicative of a very healthy run of the river by your complex. The most numerous are known as caddisflies and are in fact not flies and do not bite people or feed on plants.

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As these species are aquatic as larva there is absolutely no need to change any mulch or other vegetation/landscaping around your complex to try and reduce the numbers of caddisflies; the site of the larval habitat (their origin) is in the river. All of the species I collected are considered small to medium sized as adults and as such many of the species form large mating swarms of males that the females fly through to ’select’ a mate. The sweep samples I took on land of the swarms bear this out as they are mostly males. Most species of small to medium sized caddisflies do not feed as adults and only live about 1 week as adults, with an average of 2-3 weeks (although about 25% of species may last longer), for any one species. The species, Dolophilodes novusamericanus, which was active when Diane and I visited has listed in the literature as emerging from early May to early August but that is throughout its range in BC. I suspect that at any one site emergences are mostly done in 2-3 weeks tops. Thus I am suspicious that you have pulses of several species reaching your building over the summer as adults and forming mating swarms.

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As for distance travelled and height of flight there isn’t a huge amount of literature but there was one very good study published in the 1990’s that indicated there was an exponential decline in the number of caddisflies travelling from a river beyond 650m to a maximum of 5km— these distances are in part a reflection of the fact small to medium sized caddisflies are wind-assisted in flight distance. As well, they can get up 60m into the air column without much trouble. From these 2 facts I doubt that planting any sort of hedging/trees to act as a screen would have much effect on the number of adults you see at your building.

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The literature also indicates that caddisflies do tend to have their dispersal flights (as opposed the the mating swarms you see all day) around dawn and in the evening until about an hour after sunset. They are attracted to lighter colours such as white at those times of the day but given the location of your building relative to the river, the direction of prevailing winds, and the shear number of caddisflies emerging I’m confident that the colour of your building will not impact the number you see. The one thing you might want to examine is the use of lights around dawn and dusk. It has been shown in the literature that caddisflies are more attracted to incandescent and mercury vapour lights as opposed to LED’s — again all lights are attractive but LED’s seem to be less so. Thus you might want to investigate that if your outdoor lights are not LED’s ti might be worth switching as the current ones burn out.

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Finally there was one entire PhD thesis published in 1959 on the control of ’nuisance’ caddisfly populations in the Mississippi River drainage — they tried DDT which was very effective at killing the larva in the water. What they found was that the larva that survived did so well because there was less competition for resources the number of adults emerging didn’t really decrease. Upshot is even if there was a modern insecticide the would be allowed to used in the river you are unlikely to reduce the total number of adult caddisflies emerging.

Bottom line is you might get a few less caddisflies if you use the correct wavelength of LED’s for outdoor lighting, keep your blinds closed early morning and dusk /early in the night. Only other thing might be to encourage insectivorous birds and bats through sponsoring nest boxes/bat houses down around the river in conjunction with local nature groups. Given that DDT didn’t have much of an impact on a problem such as yours I doubt you would see a population reduction but in might provide the residents with some satisfaction to see animals around that are ‘helping’/benefit and thriving with your caddisfly issues.