APHANIPTERA FLEAS 



523 



Fia. 250.- 



-Jiystrichopsylla talpac. Britain. 

 (After Ritsema. ) 



"We all know that the Flea is so fiat, or compressed sideways, that it 



does not mind the most severe 



squeeze. This condition is 



almost peculiar to it ; a great 



flattening of the body is com- 

 mon in Insects — as is seen in 



another annoying Insect, the 



bed-bug — but the compression, 



in the flea, is in the reverse 



direction. In other respects the 



external anatomy of the flea 



shows several peculiarities, the morphological import of which has 

 not yet been elucidated. The head is of very 

 peculiar shape, small, with the antennae placed 

 in an unusual position ; the clypeus is said to 

 be entirely absent, the front legs are articulated 

 in such a manner that they have a large addi- 

 tional basal piece — called by some anatomists 

 the ischium — and in consequence appear to be 

 placed far forwards, looking as if they were 

 attached to the head; the meso- and meta- 

 thorax have certain flaps that have been con- 

 sidered to be homologues of wings; and the 

 maxillary palpi are attached to the head in 

 such a way that they appear to play the part 

 of the antennae of other Insects (Fig. 250), 

 and were actually considered to be the antennae 

 by Linnaeus, as well as others; the mouth- 

 parts themselves are differently constructed 

 from those of any other Insects.^ The maxillae 

 and labium are considered to be not only present, 

 but well developed, the former possessing palpi 

 moderately well developed, while the labial 

 palps are very large and of highly peculiar 

 form, being imperfectly transversely, jointed 



and acting as sheaths ; the mandibles are present in the form of 



1 The best general description of the external anatomy of the flea is to be found 

 in Tasohenberg, Die Flohe, 1880. The morphology is better elucidated, though still 

 incompletely, in Wagner's valuable " Aphanipterologische Studien," Sorae Soc. ent. 

 Moss xxiii. 1889, pp. 199-260, 5 plates, and O}}. cit. xxxi. 1897, pp. 655-594, 3 

 plates. Cf. also N. C. Rothschild, Nov. Zool. v. 1898, pp. 533-544, 3 plates. 



Fig. 251. — Mouth- 

 parts of a flea, Ver- 

 mipsylla alakurt 

 S . H. Unpaired 

 pricking organ ; 

 Lp. labial palp ; 

 ilcl. mandible ; 

 jlfe. maxilla ; Mxp. 

 maxillary palp. 

 (After Wagner.) 



