DONISTHORPEA. 231 



numbers, the former being uniformly small in size 68 ; and on June 

 12th, 1914, also at Woking, I observed a few large dark nigra 

 workers among the workers of a large colony of umbrata situated 

 in a sandy bank. Several workers of both species were put into a 

 small bottle and taken home ; no fighting took place, and the ants 

 lived together on friendly terms. In this latter case the nigra 

 workers were evidently the survivors of the original nigra colony 

 into which an umbrata female had been accepted. 



On September 15th, 1912, after a marriage flight of D. umbrata 

 at Seaton, Crawley observed a dealated female umbrata enter 

 a hole under a wall which proved to be one of the entrances to a nest 

 of D. nigra 63 . 



On August 27th, 1913, after a marriage flight of D. umbrata at 

 Sandown, Isle of Wight, I found a dealated female umbrata fight- 

 ing with some nigra workers on the pavement near the entrance to 

 a nest of the latter 66 ; on August 10th, 1914, I noticed a dealated 

 female umbrata, after a marriage flight at Weybridge, enter the 

 nest of a large colony of D. nigra. She forced her way past some 

 nigra workers standing at the entrance, and though I waited for 

 some time, she did not appear again. 



In August, 1896, Crawley proved by experiment that queenless 

 colonies of D. nigra will accept fertile females of D. umbrata and 

 bring up the offspring of the latter until the colony becomes a mixed 

 one of the yellow and black ants. He placed a dealated female 

 umbrata picked up near Oxford in a box with two nigra workers 

 which she immediately killed from a colony of the latter which 

 he had in captivity, containing about four hundred workers, worker 

 and female pupae, and a large quantity of eggs. She was then 

 introduced to more of the nigra workers, and when they were found 

 to be on friendly terms, they were placed near the door of the nigra 

 nest. The workers immediately entered the nest and were followed 

 in a few moments by the queen, swarms of ants collected round her 

 and saluted her. A few days later the workers killed the young 

 winged nigra females that had come to maturity in the nest. The 

 queen began to lay on January 26th, 1897, but for two years only 

 nigra workers were produced from part henogene tic eggs laid by 

 the workers so that the offspring of the umbrata queen must 

 have been devoured in the egg or larval stage. In 1899 the eggs of 

 the queen were at last allowed to reach the pupal stage, but it was 

 not till 1900 that young umbrata workers were allowed to live and 

 were unmolested, and by July 18th some twenty were present, and 

 assisted the nigra workers to tend the brood 34 . 



In 1908 similar results were obtained 47 , and as Lord Avebury 

 found that workers of D. nigra will live seven years, or more, a 

 colony of D. umbrata, therefore, founded by adoption in this 

 manner, must take more than five years to become exclusively 

 umbrata 62 . 



