346 ANNUAL REPORT SMITHSONIAN INSTITUTION^ 1915. 



blows on the plains the hollow balls, pierced with holes, give out 

 strange, low sounds recalling the whistling of wind in the rigging of 

 a ship, or the tones of an aeolian harp — hence the name, acacia- 

 flutes. 



If the eggs, larvae, or chrysalises of the ant were placed in the 

 hollow of the gall without precautions, at every puff of wind they 

 would be thrown against each other and injured. To avoid this 

 danger the ants build from the interior substance of the gall, which 

 has the appearance of an agaric fungus, a series of combs and cases 

 in which the larvae and chrysalises are placed. 



So there really exists a kind of symbiosis between the ants and 

 the acacias ; but who profits by this symbiosis ? In the galls the ants 

 find protection for themselves and their larvae ; on the other hand, 

 the ants cause no damage to the acacias and give them protection 

 against numerous enemies. Giraffes, antelopes, and gazelles are kept 

 away by the presence of these ants with such nauseous secretions. 



V. 



There are also cases in the insect world in which the adult uses 

 the larvae in the construction of the nest. This singular habit occurs 

 among certain tissued ants, CEcophylla, Camponotus, and Polyrha- 

 chis. The CEcophylla, inhabiting Asia, Africa, and Australia, build 

 their nests among the leaves of certain trees by binding the leaves 

 together with the aid of silk threads (pi. 3, fig. 1). 



Among these ants there is observed one of the most curious phe- 

 nomena of all biology. If the nest be torn in any way so that the 

 leaves are separated from each other, the ants are immediately seen 

 hurrying out. Wliile some are defending the nest against the pre- 

 sumed enemy, the others hasten to repair the damage done. From 

 one edge of the tear the workers try with their mandibles to reach the 

 edge of the neighboring leaf and draw the two edges together to 

 close the break, but the distance is often too great and they are forced 

 to form a living chain. One ant with its mandibles seizes one of its 

 comrades by the body, so that the second one may be able to reach the 

 edge of the neighboring leaf. If the distance is still too great, a 

 third comes to join the others, and sometimes the chain is made up of 

 five or six ants. This work is very fatiguing, sometimes taking sev- 

 eral hours to make sure the contact of the two leaves. The ants then 

 clean up and polish the edges of the leaves, but how can they secure 

 the necessary adherence to make the connection permanent, since the 

 adult ants do not have setiferous glands? This difficulty is overcome 

 by a method so astonishing that the first observations made in Singa- 

 pore in 1890 were doubted by naturalists. When the edges of the 

 leaves are perfectly clean several workers emerge from the nest, each 



