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[Vol. 88 
ants”. However, he could not “see the Pella eating live ants or 
fighting any of the ants on the trail”. 
Our observations of Pella funesta, P. laticollis and P. humeralis 
confirmed that these species live as scavengers, feeding on dead or 
disabled ants and debris discarded by the ants. However, we also 
observed these beetles acting as very effective predators on the ants. 
Most of the following studies were made with P. laticollis and P. 
funesta. 
During the main foraging season from May to October Lasius 
fuliginosus is active day and night. Foragers travel along well 
established trunk trails to feeding sites which are sometimes more 
than 40 m distant. At daytime we only occasionally saw Pella beetles 
moving along or nearby the trail. However, when we watched the 
trunk trails with a flash light at night many Pella were seen running 
along the ants’ foraging routes. Although most beetles were found 
within a range of 5 m from the nest tree of L. fuliginosus , we also 
found beetles on the trunk trail as far as 22 m away from the nest. 
On 6 different occasions we witnessed Pella beetles hunting L. 
fuliginosus workers at night on the foraging trail. When an ant was 
killed it was dragged a few centimeters away from the trail and eaten 
under a shelter, sometimes by several beetles simultaneously. 
More detailed observations on the behavioral interactions of 
Pella and L. fuliginosus were made in the laboratory. As long as 
enough dead ants were available at the ants’ nest midden, the beetles 
showed no predatory behavior at all, limiting themselves to a diet of 
ant cadavers (Fig. 2A). But when the beetles were starved for a few 
days and then placed together with ants in an observation arena, the 
predation by Pella became strikingly prominent, although the time 
of onset was often very unpredictable. We saw the beetles hunting 
during the daytime, but we observed such activity most frequently in 
the evening or at night. The beetles chased after individual ants and 
pursued them through approximately 2-6 cm (very rarely through 
longer distances than that). When the beetle moved directly behind 
the ant it attempted to mount it and insert its head between the ant’s 
head and thorax. When attacked the ant usually reacted by 
suddenly stopping and pressing the femur rapidly and tightly to its 
body (Fig. 5). Often this reaction threw the beetle off the back of the 
ant, allowing the ant to escape. In one series of observations we 
counted 178 beetle onslaughts on L. fuliginosus workers within a 
period of 3 hours; of these, only 9 attempts (5%) were successful. 
