SYSTEMATIC VIEW OF THE ORDER
SIPHONAPTERA

Order Siphonaptera. Latreille (1825).

Insects with body laterally compressed. Head rounded and fixed by the whole posterior part to the thorax. Mouth-parts for piercing and sucking, consisting of paired mandibles with serrate margins and unpaired labrum. These are sheathed by the labium and labial palpi. MaxillÆ usually triangular with four-jointed palpi. Eyes simple, placed in front of the antennÆ, occasionally rudimentary or absent. AntennÆ of three main segments which lie when at rest in a groove. Three thoracic segments, always free, each consisting of a notum and a sternum. The sterna of the second and third segments are further divided into a sternum, an episternum and an epimeron, the two latter constituting the pleura. Wings and rudiments of wings entirely absent. Abdomen of ten segments of which the sternite of the first segment is suppressed. Abdomen enormously swollen in pregnant females of certain species. Combs frequently present on head, thorax, and abdomen. Legs developed for leaping. Coxa powerful; femur thickened; tarsi of five segments, ending in two claws on the distal segment. Metamorphosis complete. Larva of thirteen segments. Pupa enveloped in silken cocoon. Imago a temporary parasite (usually) on warm-blooded vertebrates.

I. Family SarcopsyllidÆ. Taschenberg (1880).

Rostrum (= labium + labial palpi) rather long but very weak and pale, consisting of two or three segments inclusive of the unpaired basal segment. Genal edge of head always produced downwards into a triangular process situated behind the insertion of the maxillÆ at the ventral oral angle. Thoracical tergites together shorter than first abdominal tergite.

To this group belong the chigoes and their allies, the most truly parasitic fleas. About fourteen species have been described, which can be grouped into three genera, viz. Dermatophilus, Hectopsylla, Echidnophaga.

II. Family PulicidÆ. Taschenberg (1880).

Rostrum (= labium + labial palpi) more or less strongly chitinized, consisting, except in a few cases, of five, or more, segments inclusive of the unpaired basal one. Thoracical tergites together longer than first abdominal tergite.

Here belong the majority of Siphonaptera.

III. Family CeratopsyllidÆ. Baker (1905).

Head on each side with two flaps situated at the front oral corner. Here belong the bat-fleas only. There are several genera, and about twenty-five species have been described. In most of the bat-fleas the maxillÆ are shaped like a dumb-bell, but in the genus Thaumopsylla they are triangular as in the PulicidÆ.

Oudemans (1909) has put forward an alternative classification of the order Siphonaptera based on the morphology of the head:—I. Integricipita, II. Fracticipita.