84 HYMENOPTERA. 



occupied a bank for several years, until il has become com- 

 pletely riddled with its burrows, suddenly desert it ; the 

 same circumstance has also come under my observation with 

 a large colony o^ Euce?'a longico7mis, which quitted its long- 

 established abode on the south side of Highgate Archway, 

 and established a colony on the north side ; where, I believe, 

 it is to be found up to the present time. 



Several causes for these migrations may be suggested ; 

 where extensive colonies have for a long time existed, the 

 bank in which they burrow at last becomes, as it were, com- 

 pletely honey-combed, so that fresh space for new burrows 

 becomes exhausted ; parasites may also become so numerous, 

 and other insects so obnoxious to the bees, and so formidable 

 in numbers, that the colony is compelled to seek for new 

 and more favourable quarters. Colonies may, probably, 

 sometimes be entirely exterminated by parasitic Acari. That 

 such vvas the case with a very extensive one that formerly 

 existed at Northfleet, I have every reason to believe. 



The Acarus to which I have alluded was described by 

 Newport in the 21st volume of the Linnsan Transactions, 

 and named Meteropus ventricosa ; unfortunately the generic 

 name had been used by no less than seven previous authors; 

 I would therefore propose to substitute the generic appella- 

 tion of Nemportia, 



This extraordinary parasite is only occasionally found, 

 and, as far as my experience enables me to judge, only in 

 old, long established colonies. From the one alluded to 

 above I several times obtained larvae of Antliophora for the 

 purpose of tracing their changes, and also of rearing some 

 of the various parasites by which they are attacked. On 

 one occasion I procured upwards of a hundred, and of these, 

 full two-thirds were destroyed the following spring by this 

 exterminating Acarus. 



