1982] 
Holldobler — Cerapachys 
21 
Discussion 
Raiding expeditions in Cerapachys turneri are organized by indi- 
vidual scout ants, that return to the colony after having discovered a 
nest of the prey species. The scout lays a chemical trail with secre- 
tions from the poison gland, which serve as recruitment and orienta- 
tion signals for the nestmates. Circumstantial evidence suggests that 
in addition the scout releases a stimulating chemical recruitment 
signal from the pygidial gland. This occurs probably when the 
scouts move with their gaster held slightly upwards in a calling 
position. 
Wilson (1958) reports the field notes made by H. Potter on the 
cerapachyine species Phvracaces potteri, which contain the only 
available description of the early stages of a complete raid observed 
in the field. Before the raid started Potter noted a few workers 
moving rapidly about, “each with its abdomen raised upwards”. 
These observations match closely my findings in the laboratory and 
lend further support to the hypothesis that in addition to the trails 
laid with poison gland secretions, another stimulating signal is dis- 
charged, presumably from the pygidial gland of the recruiting ants. 
Wilson (1958) observed groups of Phvracaces moving along a 
raiding trail laid down by a raiding party on the previous day. In 
this case no individual leadership was involved and the foragers 
seemed to emerge from the nest randomly without a special recruit- 
ment stimulation by scout ants. Obviously these ants were following 
an established foraging trail, leading to a previously raided Phcidole 
nest which appeared to be vacated this time. Small exploratory 
parties conducted brief excursions to the side, but in most cases they 
turned back to the main trail. No nest suitable for raiding was found 
during these explorations. 
These observations strongly suggest that chemical trails laid dur- 
ing raiding expeditions might still function as orientation cues one 
day later and that foraging parties can follow these established trails 
without the leadership of a recruiting scout ant. Indeed, my labora- 
tory experiments with Cerapachys have demonstrated that artificial 
trails drawn with poison gland material are effective as orientation 
cues at least for several hours. 
