We have found a tunnel like cocoon in our window seal after the last winter. There is a bug in the one we collected but he wouldn't come out for his photo shoot. He is green and looks like a half ant and half fly. They have built cocoons in all of our windows. If anyone know what they are please let me know I've never seen them before and we didn't have them last year.
These are not cocoons, but brood chambers ('nests'), likely those of a leaf-cutting bee (Hymenoptera: Megachilidae - see http://tinyurl.com/mnt4za for an example. These bees will construct these brood chambers in just about any handy cavity from holes in the ground to hollow stems or even abandoned wasp nests. About the only other insect whose 'nests' have been found in window channels are grass-carrying wasps (Isodontia spp.; Hymenoptera: Sphecidae), and their structures appear quite different from those in your image - see http://tinyurl.com/mm87fw for an example.
i have the leaf cutting bee and i sat and watched it go to one of my small trees to the new growth and cut its leaf and went to my swing and found a spot and took the leaf in over and over again pretty cool i had a picture of it but cant seem to find it. i watched it for a while was real interesting
