I am currently working with the mites Dermanyssus hirundinis and Androlaelaps casalis and their effects on House Wrens. In order to identify them, I have been clearing them in 85% lactic acid (the mites, not thewrens). While examining the mites, particularly the Dermanyssus which is exclusively parasitic, I have noticed that the gut contents do not clear. Rather, they take on a dark red or black color. I am curious. Is this the bird's blood I am seeing (higher magnification reveals blood-shaped spheres) or is it an artifact of clearing? This information would be useful, as it could let me know at what stage in the wren nesting cycle the mites begin to feed. Any help would be greatly appreciated.