Asked May 26, 2017, 4:51 PM EDT

Hi there, we are wondering if you can help identify what these insects are. They are crawling and flying all over our dock, plants by the dock, and now they are in my gardens closer to the house. They have laid eggs all over our dock posts. What are they, and will they damage my perennials? How can we get rid of them? There are "smears" of egg larvae all over and under our dock. ( * see picture of one actually laying eggs on post)

Hennepin County Minnesota

6 Responses

I'm trying to see if someone else knows the id. I have had no luck yet. Can you see any damage to the plants from eating? There is an insect id site at the U of MN Extension, but I have not found a match yet. That said, I haven't had time to look at all the pictures yet. I'll let you know if I hear anything from anyone, and see if you can find a match. Also, look for eating damage on the plants.

Hi there, Wondering if you have made any progress on ID of this insect? It does not appear yet to be damaging or eating plants....however, they are not slowing down on laying eggs smears! Constantly cleaning off dock with brush and getting attacked by them! Yikes. Not fun on the dock. They seem to hide down in the bark after sunset and out during day. We have no lights down there, so attraction to light is moot. Could they have come with bark. We just re-placed all our bark with new stuff. HMMM?

Sorry, I thought I had replied to you! According to Bugguide this insect (aquatic) is probably an alderfly (Sialis sp.). According to Wiki, they are known for laying vast numbers of eggs.

Thank you! That is it!
Is there anyway to get rid of them? It looks like they emerge from April to June. Does that mean by end of June they won't be an issue?

Let me know if you can!
Thank you for your help!

Jenn Prueter

From everything I'm reading, alderflies are part of the natural ecology of springs, rivers, reservoirs, and other bodies of water and do not need to be controlled. Have you been hosing them off?

Yes, basically and washing off the eggs. No problem. Just that in 25 years of having dock...first time such a big issue.

Thank you for all your help! I am so glad my gardens not in danger.
Have great day!