INSECT VARIETY. 213 



generally correct, will render unnecessary the received physical 

 notion enunciated to satisfy the present indication of the 

 phonometer termed the syren, that requires the insect wing to 

 strike the air with enormous rapidity ; for here we have adequate 

 mechanism to produce short wave lengths and high notes, inde- 

 pendent of Aving acceleration. 



But certain species in these diaphanous-winged orders afford 

 proof of the existence of a voluntary spiracular music. Thus 

 the majority of the ornamental trihe of Hover Flies when 

 captured, emit acute high notes in the gamut of a singing 

 tea-kettle, slightly vibrating the shut wings, or retaining them 

 in perfect repose. The Drone Flies, the Wasp Flies, with the 

 smaller Si/nlla pipiens, readily so perform; and among the bees 

 we recognise these notes in the Sand Wasps, the Bumbles, and 

 others. These, as the former, produce it with the wings closed 

 over the back, either motionless or vibrating slightly to tho 

 thoracic muscles, the potency of whose play may be experienced 

 as a species of electric shock by applying a pencil to the part. 

 In bees a respiratory movement, an elongation and contraction 

 of the abdomen, invariably accompanies this music, due to the 

 chitineous plates covering the pedicled abdomen sliding one 

 within the other telescopically. We may observe this singular 

 action of pumping in air in both bees and beetles when inflating 

 previous to flight, the abdominal distention being allowed for 

 by intersegmental membrane; and, as we have seen likewise, 

 this is often the movement of stridulation in the same orders. 



Having treated of the existence and manner of production, 

 we now come to the range of expression and import of vocal 

 music. The British Diptera most noted for their humming or 

 buzzing notes are the Gnats or Musquitoes, the two classes of 

 Cattle FKes, the Mottled Clegs or Forest Flies, the vernal, flower- 

 visiting Bee Flies, the road-settling Hornet Flies {Asilius, 

 Lin.), the many genera of sparkling Hover Flies, the unpreten- 

 tious Stinging Flies {Stomox//s, Fab.), too often mistaken for their 

 House Fly prototype, the species of TacJiirm, and the swarms of 

 carcase and other domestic, refuse-born kinds, that haunt our 

 apartments and back courts. Yet although we may at times 

 observe the note of a fly who impels his companion on the break- 

 fast cloth takes unwonted shrillness, or that incensed gnats 



