264 BRITISH ANTS. 



The top line represents five different colonies, starting with rufa 

 and gradually passing into pratensis, and it is understood that all 

 the individuals in each colony belong to the same race, or form of 

 variety, whichever it may be. 



The side line represents the different embryological forms which 

 may occur in each colony. Forel's intermediate forms between the 

 worker and female are what are now called pseudogynes. 



It is not however always the case with rufo-pratensis that only 

 one variety is found in the same colony ; Forel himself states that 

 once or twice he has seen typical individuals and others distinctly 

 passing to a neighbouring form in the same colony. He once sent 

 two rufo-pratensis workers, taken in the same colony and mounted 

 on the same pin, to an emerited myrmecologist, and the latter 

 stood him out that the one was F, rufa and the other F. pratensis. 

 Forel says : " I hardly think that I have succeeded in convincing 

 him of the fact." 1 



Wasmann says : " It remains still to be settled whether the 

 intermediates between the two races rest on direct variation, or 

 rather on crossing between the pure races of rufa and pratensis. 

 I am rather inclined to the latter opinion." 6 



I believe that in localities such as the Isle of Wight, where rufo- 

 pratensis is found, but where pratensis does not, and has never been 

 known to, occur, the former rests on direct variation from rufa 

 proper, and in these cases the variety is found to be much nearer 

 to rufa ; whereas in the Highlands, where both rufa and pratensis 

 are present, the varieties have chiefly sprung from crossing between 

 rufa and pratensis males and females. We have already seen, under 

 rufa, that colonies of rufa, pratensis, and rufo-pratensis will each 

 receive the other's queens after the marriage flight, and a combina- 

 tion of all these facts will alone explain the contents of some of the 

 nests I have seen from Nethy Bridge. 



In 1909 1 recorded rufo-pratensis from Nethy Bridge, the colouring 

 of the ants being darker than that of rufa, but they did not possess 

 the hairiness of pratensis, and I mentioned that the nests differed 

 somewhat from those of rufa, being more compact, the dome- 

 shaped surface smoother and flatter, and the nest material not so 

 loose capable of being moved in layers. A point which struck me 

 very much was the way in which many of the nests were being 

 extinguished by the undergrowth. Moss starts to grow round the 

 base of the nests, then " bilberry " and heather, which creep up- 

 wards all round the hillock, gradually driving the ants to the 

 summit, and eventually extinguishing the colony. Most of the 

 hillocks in the valley covered with dense undergrowth have once 

 been ants' nests 7 . 



On September 8th, 1912, 1 found two nests of this variety at Park- 

 hurst Forest, Isle of Wight, which were situated on a bank, con- 

 structed of finer materials than the rufa nests in the neighbourhood, 



