Question
The leaves that are falling from our maple have thousands of very bright green tiny insects. Under a magnifying glass they look like a worm with 3 legs on each side and 2 antennas in the front. They are feeding on the fallen maple leaves. The thing that is confusing to me is that only the leaves near large fir trees seem to be infested. Any clue what they are? I checked the Internet and my Landscape plant problems from washington State University. Are they Balsam twig aphids or maple leafhoppers?I am trying to keep the leaves picked up so there won't be as big a problem next year.

Thank you in advance for your assistance.     

Ruthanne

Answer
Sounds like an aphid. There has been an aphid on Big leaf Maple called  Drepanosiphum oregonensis. Drepanosiphum oregonensis, was first discovered on this tree in North America. Unknown until its discovery on the bigleaf maple, this aphid is native to the eastern Mediterranean (van Gelderen et al. 1994).
Aphids suck the plant juices from the plant and secrete a sticky substance called honeydew. If it is aphids the leaves should be sticky. The aphids will be on the leaves on the tree and any treatment would have to be done to the foliage of the tree. This late in the year i would not treat since the leaves will be falling soon. Picking the leaves up may not effect the problem next year--most aphids over winter as eggs on the twigs near leaf buds so they can hatch the following year and infest the foliage.  
I would recommend that you get the Washington Extension Service to come take a look since this is a imported insect. Their web link to the contact page is
http://ext.wsu.edu/locations/