AMKllICAN IIYMENOPTERA. 277 



somewliat from their stores, and no loss is wrouglit to the eoninion- 

 vvealtii. besides, it seems probable that the instinct which urges the 

 repletes to gather store for the larvae, nymphs and other dependents, 

 might effectually prevent them from yielding such store to any others, 

 after the formicary had been reached. It may be supposed, since ant 

 nature is not unlike human nature in some respects, that the surplus 

 honey-dew, after feeding the dependents, would be kept for individual 

 delectation, and thus the builders and sentinels be compelled to leave 

 their work, and forage for themselves. The general movement, there- 

 fore, to arrest the repletes at the stations near the feeding grounds is 

 evidently for the public good. 



Seulinels.— I observed on the tree-paths a movement that had the 

 appearance of some policy of police. Workers, with the normal round 

 black abdomen, were scattered at intervals along the trunk. They did 

 not seem to belong to the line of ascending foragers, but rather to be 

 stationary, as tlnjugh they were sentinels or policemen. They were 

 active in challenging with their antennae the repletes who were on the 

 return, and were quick to resent any interference made by intruding a 

 finger or straw upon the path. This statement is made with reservation 

 as I was not able fully to satisfy myself that the facts levealed a fixed 

 habit. The point, however, is well worthy of future investigation. 

 There is at least a probability, from analagous habits of the ant, that 

 the individuals referred to above were indeed sentinels as their be- 

 haviour indicated. It is a well established fact, in the economy of ant 

 hills, that sentinels are posted at or near the entrances, and connnoa 

 avenues of approach. I satisfied myself of this by very many observa- 

 tions and experiments which it is not necessary to relate in detail. It 

 will suffice to say that on every occasion of approach of any object to 

 a hill or entrance, workers instantly sprang upon the surface. These 

 sentries were constantly seen lurking just inside the gallery doors, 

 whence they issued with every mark of intense vigilance and excite- 

 ment the moment a finger was intruded or the smallest object dropped 

 near them. Fre((uently they patrolled the vicinity of the gates. They^ 

 attacked every intruder with the utmost promptness and intrepedity. 

 It gave subject for great wonder to note the rapidity with which an 

 alarm was communicated throughout a large hill. Two hills in par- 

 ticular, whose inhabitants were for several days in a condition of high 

 nervous excitement, attracted attention. Standing a yard or more 

 from the base, l would agitate with my foot a stone which evidently 

 had communication with the interior of the mound. There was scarcely 



TRANS. AMEK. ENT. SOC. VI. (37) NOVEMBER 1877. 



