24 



AN ACCOUNT OF BBITISH FLIES. 



Genus i. — Pulex. 



Characters of the Genus. — Body oval and compressed, and covered 

 by a hard, chitinous integument, which is covered by hairs and 

 bristles on the back and legs. There are thirteen segments, and 

 they are continuous, there being no distinction into thorax and 

 abdomen. 



Head small. Mouth suctorial. Upper lip obsolete (unless the 

 lingua represents it). The mandibles are in the form of two fiat 

 setae, with a central rib and serrated edges. The lingua is the same 

 length as the mandibles, the three forming a piercing, or puncturing 



Fig. 3. — Imago of Pulex 9- — ti, antennae; vit, maxillary palpi ; i, ii, Hi, pro- 

 meso-, and meta-thorax. 



organ. When at rest these organs are closed by the labial palpi, 

 which form a tubular haustellum. These arise from a small labium, 

 which comes from a very small mentum. 



The maxillae are sub-triangular appendages, and are coriaceous 

 and are situated at the side of the mouth. They have large maxillary 

 palpi arising from the base, composed of four joints, and formerly 

 mistaken for antennae. 



Eyes small ( = simple oceUi) and round. Antennae are placed in 

 pits behind the eyes. These pits are covered by movable valves. 

 At times the antennae may be withdrawn out of these cavities. 

 They are four-jointed appendages, the third joint being small and 

 cup-shaped. The terminal joint is often transversely striated.* They 

 vary in different species. 



The thorax is composed of three typical segments, but more 

 distinctly marked than in other insects. On the second, or meso- 

 thoracic, is the first pair of scales, or rudimentary wings, and on the 

 metathoracic segment we find the large scales representing the hind 



* These striations are really joints. 



