216 THE CAUSES WHICH PROPAGATE 



articulation at the root of the wings, and when the wing is very 

 slowly moved up and down each time there originates a sound, 

 which clearly results • from the wing- roots jerking on the pro- 

 thorax during their descent, a second note succeeding the first 

 when the wings have attained their lowest posture. The crack- 

 ling sounds follow quick on one another, and originate the 

 stridulation, soon to be drowned in the notes of the vibrating 

 wing/' In addition to the instances preferred, I have heard 

 the primitive spiracular notes of the Hover Flies given out by 

 a showy northern species, Sericomya borealis (Plate IV., Fig. 7), 

 that frequents brambles in the West Highlands, as it alighted on 

 rotten stumps with closed wings, to fulfil the maternal duty of 

 oviposition : others emit them, I believe, when simply sunning 

 themselves, a joyous sound harmonising with the country air. 



In Bees, especially when apterous, the filiform character of 

 the antennse allows the development of a language of touch, and 

 there are also instrumental performers. But with the aerial 

 species no medium is more suitable for intercommunication than 

 that various and varying hum that falls so pleasantly on the ear 

 whether overshadowed by the palm, the vine, or the sallow. 

 Among northern Hymenoptera most noticeable for their summer 

 notes are the genera Sirex, Bembex, Saropoda, Dasypoda, Vespa, 

 Crabro, Apis, Bombus, &c. 



The modulation this music is susceptible of, expressive of 

 fear, anger, or pleasure, did not escape the attention of John 

 Hunter. Hive Bees may, he says, be said to have a voice. 

 '' They are certainly capable of forming several sounds. They 

 •give a sound when flying which they can vary according to 

 circumstances. One accustomed to bees can immediately tell 

 Avhen a bee makes an attack by the sound, which is a very 

 different noise from that of the wings when coming home of a 

 fine evening loaded with farina or honey ; it is then a soft 

 contented noise. They may also be seen at the door of their 

 hive, with the belly rather raised, and moving their wings, 

 making a noise.''* The male Hive Bee or drone, and the 

 females, queens and workers, can also severally be distinguished 

 by the timbre of their music. 



Then, as we have already seen, the primitive spiracular note 

 * Fhilosoph. Tram., Vol. LXXXII., p. 182 (1792). 



