Recent (after Snograss, 1946) studies of flea morphology were devoted to the anatomy and sensory organs of different imago segments. The head anatomy were studied in a number of species of fleas (Wenk, 1953; Amrine and Lewis, 1978; Wachmann, 1972). Comparative studies have been made of the structure of mouth apparatus (Vashchonok, 1983), antennae (Rothschild, Hinton, 1968; Medvedev, 1982, 1983) and head capsule (Medvedev, 1989a, b). The anatomy Xenopsylla cheopis thorax was studied mostly detail (Lewis, 1961; Rothschild, Schlein, 1975). Comparative studies of thorax were done by Medvedev (1990, 1992a, b).
The genital apparatus (aedeagus and modified abdominal segments) of fleas is described in detail in a number of studies (Peus, 1955; Smit, 1970; Rothschild, Traub, 1971). Gunther (1961) described the genital musculature of fleas. Goncharov (1964) and a number of other workers studied the functions of various genital structures. Others (Traub 1950; Mardon, 1978; Cheetham, 1988) have made a comparative anatomical study of the aedeagus. Scanninig electron microscopy has been used for aedeagus studying (Medvedev, 1984; Cheetham, 1988). This technique and together with light microscope were used in the comparative investigations of the aedeagus of many species of fleas (Medvedev, 1993, 1994).