47 



Janet nest, of which the first chamber was occupied by five 

 F. fusco-rufibarbis workers, two females, and a number of worker 

 and female pupœ. One of the F. rufa females invaded their 

 chamber and eventually killed all the workers. Later on a 

 number of pupie were found in the chamber occupied by the 

 three F. rufa females, a female being seen on several occasions 

 carr}ing pupae in. The stolen pupie in all numbered fort}'-two, 

 including two female ones. Finally one of the F. fusco-rufibarbis 

 females was found in the F. rufa chamber, and the other was 

 being carried in by a F. rufa female. The two F. fusco-rufibarbis 

 females were then left alone and uninjured, but died in a few 

 days' time. 



On June 17th, 1912, Crawley placed two old queens of F. 

 fusca, V. glebaria, in one dark chamber of a two-chambered plaster 

 nest. A deälated fertile female of F. rufa, picked up at Woking 

 after the marriage-flight, was placed in the other and light 

 chamber. She soon entered the dark chamber and approached 

 the two F. glebaria females, who threatened her. She entered 

 their compartment several times, but continually meeting with 

 hostiUty, returned to her own, where she remained for some 

 days, till the termination of the experiment. 



Temporary Social Parasitism in the Genus Lasius 



It is established without doubt, not only from the experiments 

 to be outlined below, but also from numerous observations in 

 nature, that Temporary Social Parasitism exists in an advanced 

 stage among certain species of Lasius, viz. unibratiis, mixtus 

 (and probably the others of this group), and fuliginosus. 



The females of these species have proportionately smaller 

 abdomens than those of L. flavus, L. niger, etc., which found their 

 colonies unaided, and some [e.g. fuliginosus) are considerably 

 smaller altogether in comparison with their workers. They 

 also share the peculiarity of possessing large, broad heads. So 

 far as we are aware, the first instance of a mixed colon\- of Lasius 

 was that observed in Sweden by Adlerz, in 1895. He found a 

 L. niger colony containing a number of L. flavus workers which 

 assisted the L. niger workers to carr^'oñ the brood. As Wasmann 

 suggests, the workers that Adlerz took to be L. flavus were 



