50 HrMBLE CREATURES. 



the Butterfly, Beetle, Dragon-fly, &c., the second pair 

 is situated upon the metathorax, the third ring; hut 

 in the Fly, which is only furnished with one pair, the 

 place of the second is supplied by two little members 

 termed halteres, or poisers. These appear to be rudi- 

 mentary wings, are protected by a pair of horny scales, 

 and, seen with the naked eye, they resemble two 

 globules, which are kept in a state of constant vibration 

 whilst the insect is on the wing. On being detached, 

 however, and examined under the microscope, they pre- 

 sent a clubshaped appearance (PL VI. fig. 3), and their 

 base is found to be studded all over with microscopic 

 vesicles disposed in regular rows upon the surface. 

 Between these vesicles, as in the case of the antennae, 

 numerous hairs are interspersed vrith great regularity. 

 It has been found that two large nerves proceed from 

 one of the principal nervous centres in the insect (the 

 thoracic ganglion) into the halteres ; and from these, 

 minute branches have been traced to all the vesicles 

 upon the surface : from this it must be inferred that 

 these vesicles (as well as those in the wings, with 

 which nerve-fibres also communicate) are organs of 

 sense, and it is believed by the observers who dis- 

 covered them* that they are the organs of smell. 

 Should this prove to be the case, there will be leas 

 difiiculty in determining the true character of the 

 antennse, in which the vesicles are depressed, as stated 



• Mr. Pm'kiss and Dr. J. B. Hicks : see papers by latter in the 

 Journal of the Linuean Society, vol. i. No. 3 ; and Linnean 

 Society Transactions, vol. xxii. p. 144. 



