Img 1 Cat flea cocoon size: 5 x 2 millimeters.
Cat flea cocoons are 4 to 5 millimeters long, and 2 millimeters wide. For comparison, large sesame seeds are 3.5 millimeters in diameter.
Larvae Size at Cocoon Formation
Larval cat fleas grow to be 4-5 mm long, and 0.5 mm wide. The larvae fold themselves in half when they form cocoons, and remain folded inside the completed structures. They’re referred to a U-shaped or V-shaped larvae. A doubled-over, U-shaped larvae measures 2.5 by 1 mm.
While bent in half, a flea larva will spin sticky silk fibers around itself. Debris from environment (e.g. sand and dust) readily adheres to the moist silk. The accumulated detritus on the silk increases the size the cocoon, adding about a millimeter to the thickness of the walls. With all components combined (larva, silk, and debris), the final cocoon is four to five mm long, and two mm wide.