I've been sanding filler for several days, and in the process have crushed thousands of tiny black flying insects. These are so small I don't see them until they sit down on the filler. The canoe looks like I took a pepper shaker and seasoned it liberally, except that the pepper is moving. I have to assume they are being attracted by something in the filler - the odor of linseed oil perhaps? This has occurred during daylight, in the sun, as well as in the garage in shadows during the day. Has anyone had a similar experience? I've not considered adding DEET to filler until now . TM...