^18 THE CAUSES WHICH PROPAGATE 



uttered hy the female of a Mason Bee {A>if/iop/io)-a jjariefina) 

 is recorded as having- brought its offended males around an 

 audacious captor. 



But most frequently this music is observed in another group 

 of the bee kind, where the first segment of the thorax is 

 narrowed in front into the form of a knot or joint, and the first 

 ring of the abdomen, and sometimes even the second, is 

 narrowed to an elongated pedicle, so that the hind body is, as it 

 were, hung by a stalk or thread. The females of the species of 

 Sphex, or Sand Wasp, agree with this description ; and those 

 who on arenaceous soils watch these tunnel their holes in the 

 shifting bank, and successively close them with some insect 

 carcase to nourish their future progeny, repeatedly observe them 

 uttering their ^Eolian trill, with their wings folded in repose or im- 

 jierceptibly vibrating, producing spiracular notes which have been 

 described as lying somewhere between the music of the common 

 little dipteron, S^rilla pipiens, and the stridor of a small locust."^ 

 Their wasp-like relatives, Pelopeus, one black kind of which is 

 omnij^resent on the roads in Northern Italy, hum a similar 

 brief bee tune when scraping up mud for their dauby clay- 

 nests beneath the ledges and eaves ; a proceeding which doubt- 

 less afforded Virgil the eccentric idea of bees gathering ballast 

 to steer in the wind's eye. The music in this case ajDproaches 

 the whine of a Bumble in colour. 



The wing movement in most insects is accompanied with a 

 sound. Hawk Moths that hover over flowers hum in flight. 

 A buzz is more characteristic of the night-fliers, whose tattoo 

 is so often heard at twilight on the window-pane, or during a 

 blind career over the ceiling of apartments that look out on a 

 garden. That these sounds are in part spiracular is more than 

 conjectural, as may be shown by clipping the wings of various 

 moths, when the hum or buzz becomes higher and higher, till 

 it resembles that of the Cttlices, but continues as the wing-roots 

 are capable of motion. 



Many beetles have a sonorous flight, drone, and boom ; and 



* Goureau, Ann. de la Soe. Ent. de France, b. \i., p. 397. There is a 

 description of the way the Wasp Ichneumons (Sphex Jiavipennis, albisecta, &c.) 

 tunnel in sandy soil and store insect carcases for their young, in the "Naturhist. 

 Tidsskrift. And. Eak.," p. 34. 



