FORMICA. 289 



bankment of the railway in a great state of excitement, all running 

 about outside the nest, and very active in the hot sunshine, some 

 winged females being also present outside. I then noticed that a 

 lot of sanguined workers kept arriving, carrying pupae, whilst others 

 were all hurrying off in the opposite direction. These I started to 

 follow, and found they went along the embankment for a good 

 many yards, and then descended the steep bank, crossed the 

 railway-lines in a slanting direction, and mounted the bank on the 

 opposite side. At the top I found them busily engaged in ravaging 

 a nest of Formica fusca. Many workers, laden with pupae, were 

 streaming off in the direction of their home ; I had met specimens 

 carrying pupae all the time I was tracking the outgoing ants. 

 Others were attacking and killing solitary fusca workers. Several 

 fusca workers were observed up the grass-stems, etc., holding pupae, 

 and endeavouring to escape from the slave -raiders. I watched these 

 proceedings for a considerable time, and accompanied some of the 

 ants with pupae back to their nest, quite a distance off, though they 

 covered the ground very quickly. Several trains passed, but the 

 ants did not appear to be disturbed, as when I went on the lines 

 after one had gone through, the ants continued to cross the railway 

 as if nothing had happened. It was unfortunate that I did not 

 witness the start of the expedition, only arriving after the proceed- 

 ings were in full swing." 64 



Also on July 15th, 1912, at Wey bridge, I observed a number of 

 sanguinea workers returning to their nest with fusca cocoons in their 

 jaws. A few fusca workers were noticed in the neighbourhood in 

 flight and on the top of grass-stems, some with their own cocoons in 

 their jaws, so evidently a genuine slave-raid had taken place 76 . 



These slave -making expeditions take place in July and August 

 when the males and winged females of the slave species have usually 

 left their nests, and only dealated females, workers, and worker 

 cocoons are present. Both Huber 3 and Darwin 34 assert that males 

 and winged females of the slave species are never met with in 

 sanguinea nests, but this is not absolutely the case, as Morice found 

 four males and two winged females of fusca in a sanguinea nest 

 at Weybridge on July 1st, 1900 47 , and Barnes dug up a winged 

 fusca female in a sanguinea nest at Wellington College on September 

 6th, 1902 48 . 



According to Forel raids generally take place at eleven o'clock in 

 the morning, but may occur at twelve, one, or two, and sometimes 

 as late as three or four in the afternoon 24 , and not more than two 

 or three expeditions are undertaken by one colony in one year. 



The exact position of the slave nest must have been previously 

 ascertained by single sanguinea workers, scouting independently, 

 for when the expedition starts the leaders curiously enough keep 

 falling to the rear, others taking their place, and as the ants proceed 

 straight in the direction of the nest to be robbed, a number of 





