HONEY ANTS. 



375 



long periods during which not only these substances, but also insect 

 food are unobtainable. The honey is stored in the living reservoirs 

 for the purpose of tiding over such periods of scarcity, and the ants 

 remain in their nests because they do not need to forage. Hence the 

 confinement mentioned by Forel is not the immediate but one of the 

 ulterior effects of drought. I am convinced from my observations on 

 desert ants that no amount of drought will keep these insects in their 

 nest when they are in need of food. 



While excavating the nests of M. horti-deorum 1 was impressed 

 with certain peculiarities in their structure and situation, which seem 

 to be explainable only as adapta- 

 tions to the development of re- 

 pletes. One of these peculiarities 

 is the great hardness of the soil 

 that is preferred by the ants. This 

 is the more astonishing because the 

 workers are very slender and deli- 

 cate organisms. It is evident that 

 such soil is well adapted to the con- 

 struction of vaulted chambers like 

 those in which the repletes hang, 

 whereas soft or friable soil would 

 be most unsuitable. The develop- 

 ment of repletes also makes it 

 necessary for the ants to seek very 

 dry situations for their nests. 

 Hence we always find them, in the 

 environs of Manitou at least, on 

 the summits of ridges which shed 

 the rain very rapidly. The honey 

 chambers must be kept very dry, 

 both to prevent the disastrous re- 

 sults of crumbling and slipping walls and to obviate the growth of 

 moulds on the repletes, which are, of course, imprisoned for life in 

 dark cavities and filled with substances that are favorable to the 

 development of fungi. I believe also that the size of the nest openings 

 and galleries, which are so much larger than would seem to be required 

 by such small, slender ants, may be an adaptation to securing plenty 

 of fresh air in the honey chambers. If these suppositions are correct, 

 there is obviously a reciprocal relation between the replete habit and 

 an arid environment : the ants store honey because they are living in 



FIG. 222. Galls of Holcaspis per- 

 niciosiis on twigs of Querciis nndulata, 

 showing the exuding droplets which are 

 collected by the workers of Myrmeco- 

 cystns horti-deorum. (Original.) 



