Preparation and examination of flea larvae (Siphonaptera) by light and electron microscopy

Techniques are described for making permanent slide-mounted specimens. Larvae were thoroughly macerated in KOH to remove soft internal tissue, yielding specimens with enhanced transparency and allowing examination of most of the exoskeleton in a single larva. Fatty material was removed in acetone to eliminate confusion of fat globules with sensilla in the cuticle. The more sclerotized exoskeletal elements, such as integumentary scales and the body sclerites together with their setae and sensilla, were highlighted by staining with carbol fuchsin. Resolution of numbers and arrangement of setae, especially those on the dorsum of the head capsule, in the anal comb, and on the anal mounds, was greatly facilitated by mounting larvae in dorsal orientation. Clearer views of the antennae and mouthparts were obtained, in orientations seldom achieved in whole mounts, by dissecting the head capsule. Discrimination of many taxonomically valuable features was enhanced by the use of phase-contrast microscopy. Interpretation of structures noted in light microscopy was complemented using scanning electron microscopy. The latter allowed differentiation between surface and internal cuticular structures.