CLASSIFICATION OF INSECTS. 251 



faiina : when running on the skin, causes an 

 intolerable itching. Thrips. 



815. Bee-parasites {Sti/lopiies). Larva apod, 

 with a corneous head : inhabits the bodies of bees 

 in the imago state, the head of the larva projecting 

 between the segments. Pupa changes in the 

 same situations ; the mode of change not having 

 been yet satisfactorily ascertained. 



816. The parts of the mouth of this curious 

 insect, as far as we know them, are these : man- 

 dibles elongate, linear, without horizontal motion ; 

 maxillary feeler fully developed, but the maxillae 

 very minute ; labium distinct and triangular, but 

 the labial feelers obsolete. 



817. The prothorax is a very slender segment, 

 almost lost in the mesothorax ; the mesothorax is 

 large and conspicuous, having its scutellum remark? 

 ably elongate and developed ; the anterior part of 

 this segment bears two very remarkable appen- 

 dages, which the insect keeps in constant motion ; 

 behind these appendages are the fore wings, which 

 are membranaceous, ample, and fold horizontally. 



818. The metathorax is a minor, yet very 

 apparent segment : it protrudes on each side of 

 the scutellum of the mesothorax, and bears a pair 

 of crumpled o])aque wings, which are somewhat 

 pedunculated, and much resemble the halteres of 

 some flies. Stylops. 



819. Fleas {Pulicites) constitute another very 

 curious order. Larva elongate, slender, parasitic 



