70 ANTS — BEES. 



Mutilla, and here also he found a fully developed 

 stridulating apparatus. 



He then turned to the true ants, and here also he 

 found a similar rasp-like organ in the same situation. It 

 is indeed true that ants produce no sounds which are 

 audible by us ; still, when we find that certain allied 

 insects do produce sounds appreciable to us by rubbing 

 the abdominal segments one over the other, and when 

 we find, in smaller species, an entirely similar structure, 

 it certainly seems reasonable to conclude that these 

 latter also do produce sounds, even though we cannot 

 hear them. Landois describes the structure in the 

 workers of Lasius fuliginosus as having twenty ribs in 

 a breadth of 'IS of a millimeter. In Lasius fiavus I 

 found about ten well-marked ribs, occupying a length 

 of j-Jq- of an inch. Similar ridges also occur between 

 the following segments. 



In the flies (Diptera) and dragon-flies (Libellulina), 

 the four thoracic spiracles produce sounds ; while in 

 Hymenoptera, as, for instance, in the humble bee 

 (Bombus), the abdominal spiracles are also musical. 

 The sounds produced by the wings are constant in 

 each species, excepting where there are (as in Bombus) 

 individuals of very different sizes. In these the 

 larger specimens give generally a higher note. Thus 

 the comparatively small male of Bomhus terrestris 

 hums on A', while the large female hums a whole 

 octave higher. There are, however, small species 

 which give a deeper note than larger ones, on account 

 of the wing-vibrations not being of the same number 

 in a given time. Moreover, a tired insect produces a 

 somewhat different note from one that is fresh, on 

 account of the vibrations being slower. 



