8o HYMENOPTERA chap. 



they succumb to adversity. The young females, however, hiber- 

 nate, and each one that lives through the winter is the potential 

 founder of a new nest in the way we have already described. It 

 might be supposed that in tropical countries where no cold 

 season occurs the phenomena would be different, that the colonies 

 would be permanent, and that the nests would be inhabited until 

 they were worn out. De Saussure, however, informs us that this 

 is not the case, but that in the tropics also the colonies die off 

 annually. " The nests are abandoned," he says, " without it being 

 possible to discover the reason, for apparently neither diminution 

 of temperature nor scarcity of food cause them (the Insects) to 

 suffer. One is tempted to suppose that the death of the Insects 

 is the result of a pliysiological necessity." 



Nests of Social Wasps. — In Europe wasps' nests disappear 

 very soon after they are deserted. As it would appear from de 

 Saussure's conclusions that in the tropics as w^ell as in the temperate 

 reo-ions the rule is that the colonies endure only a portion of one 

 year, and that a new nest is commenced by a single founder once 

 in twelve months, it is a somewhat remarkable fact that some 

 tropical wasp-nests are much more durable than the lives of the 

 inhabitants require, so that solidly constructed nests are often 

 found hanging to the trees long after they have been deserted, 

 and are sometimes overgrown w^ith moss. Cuming has recorded 

 the fact that he found in South America an old wasp-nest that had 

 been taken possession of by swallows. We do not assign, how- 

 ever, much importance to the views of de Saussure, because we 

 may anticipate that enquiry will reveal inuch variety in the 

 lial)its of tropical and sub-tropical wasps. It is known that 

 species exist that store up honey, after the fashion of bees, and 

 von Ihering has recently shown ^ that in Brazil, species of several 

 genera form new colonies l;)y swarming, after the manner of bees. 

 So that it is possible that certain colonies may remain for a long 

 period in the same nest. 



Much more variety exists in wasps' nests than would be sup- 

 posed probable; those formed by some of the tropical species of 

 Vespidae are enveloped in so solid and beautifully constructed an 

 envelope of papier-mache, that they resist with complete success 

 the torrential rains of the tropics ; while some of those found in 

 our own country are made of extremely soft and delicate paper, 



^ ZooJ. Anz. xix. 1896, p. 449. See also note, antca, \k 70. 



