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).
The head capsule of fleas is very modified. It is high, narrow and cuneate. The propleurosternum covers the head from below to the peristomal aperture, as result of which it is immobile.
The antennae of fleas are in antennal fossae. The antennal fossa divide the head into anterior and posterior parts.
The thorax consists of three modified segments. They are luck wings, but have long legs. The hind legs are the principal jumping organs.
The abdomen of the adult flea includes 10 segments.
The genital apparatus of male fleas consists of the aedeagus, modified tergites and sternites of the 8th and 9th abdominal segments and claspers. The aedeagus and claspers derive from primary phallic lobe (Snodgrass, 1946, 1957; Gunther, 1961). The modified tergites and sternites of flea's belong to abdominal segments 7-9. More than 50 terms are used to describe the structures of the genitalia. The complexity of the aedeagual structure is caused by the separation of its internal duct (endophallus) into a number of complex sclerites. In addition, the eternal walls of mesomeres form the apodeme, fulcrum, and palliolum of the aedeagus.