112 Journal New York Entomological Society. ['^'°1- >^^^^, 



fore 2.30 P. M.^ The four sorties of hreviccps observed near Fallen 

 Leaf Lake occurred at 4.10, 3.35, 4.15 and 3 P. M., and the three 

 armies merely seen returning to the nest July 22, 25 and 29, could 

 hardly have started out before 3 P. M. In this connection I may 

 mention, also, that the two forays of the small shining P. rnfescens 

 laviccps Wheeler which I observed July 20, 1914, on the slopes of Mt. 

 Tamalpais, near San Francisco, Calif., must have left their nests after 

 3 P. AL How are we to account for this difference in time of sortie 

 between the Californian amazons and those of Colorado, Illinois, 

 Pennsylvania and New York? 



Before attempting to answer this question it will be advisable to 

 glance at some of the published accounts of the typical European P. 

 rufescens. The most comprehensive observations on this ant have 

 been made by Forel in Switzerland.^ During 33 days he saw a single 

 rufescens colony make 44 expeditions and estimated that the ants 

 secured from the various plundered colonies of F. fiisca and rufibarbis, 

 on these and other expeditions, which he did not observe, a total of 

 fully 40,000 larvae and pupae. Concerning the time of sortie in gen- 

 eral he writes (p. 289) : "As Huber says, P. rufescens nearly always 

 leaves its nest in the afternoon between 2 and 5 o'clock. Von Hagens 

 saw a sortie at 6 P. M.; I have observed two at 1.30 P. M. These 

 are, to my knowledge, the extreme cases. Expeditions have never 

 been observed in the morning. Ebrard says that they depart very late 

 on their first expedition (during June) and thereafter a little earlier 

 each day. I have never observed anything of the kind. I have seen 

 amazons from two different formicaries departing at 2.15 P. M. and 

 at 4 P. M. respectively. On the other hand I have seen amazons of 

 the same colony depart on several successive raids at the same hour. 

 The hour of departure depends as a rule on the temperature; the 

 warmer it is. the later do the amazons depart and znce versa. The 

 amazons of the same formicary departed during one year as follows: 

 July I, 3.15 P. M.; July 23, 5 P. M. ; Aug. 10, 3 P. M.; Aug. 12, 1.30 

 P. M. ; Aug. 14, 4.45 P. M., etc. The departure of Aug. 10 and 12 

 coincided with a pronounced and sudden drop, that of Aug. 14 with a 

 pronounced rise of temperature. According to the formicaries, the 



3 " A Slave-making Foray of the Shining Amazon (Polyergiis hicidus 

 Mayr)," Journ. N. Y. Ent. Soc, 16, 1908. pp. 144-151. 

 * Fourmis da la Suisse, 1874. 



