PETS. 77 



ants, but while some associate with several species, 

 many are confined to a few or even to one. 



V. Hagens is of opinion l that in some of these 

 beetles which frequent the nests of two or more species 

 of ant, varieties have been produced. Thus he has 

 observed that the specimens of Thiasophila angulata 

 in nests of Formica congerens are darker than those 

 found with F. exsecta. Hetcerius sesquicornis found 

 with Lasius niger and Tapi/nama erraticum are 

 smaller than those which occur in the nests of larger 

 ants ; and the form of Dinarda dentate^ which is met 

 with in nests of F. sanguinea, has rather wider wing- 

 cases than the normal type. 



I would by no means intend to imply that the 

 relations between ants and the other insects which 

 live with them are exhausted by the above suggestions. 

 On the contrary, various other reasons may be imagined 

 which may render the presence of these insects useful 

 or agreeable to the ants. For instance, they may emit 

 an odour which is pleasant to the ants. Again, Mr. 

 Francis Galton has, I think, rendered it very probable 

 that some of our domestic animals were kept as pets 

 before they were made of any use. Unlikely as this 

 may appear in some cases, for instance in the pig, we 

 know as a fact that pigs are often kept by savages as 

 pets. I would not put it forward as a suggestion 

 which can be supported by any solid reasoning, but it 



1 Berlin, Bnt. Zcit. 1865, p. 108. 



