Swarm and pseudoscorpions

Ellingsenius fulleri is the most frequently encountered pseudoscorpion species of the family Cheliferidae in South Africa. This arthropod is considered a predator of small mites and wax moth larvae found in debris at the bottom of beehives. They often attach themselves to the legs of bees and thus appear to spread to other colonies.

During swarming, thousands of bees leave their hive and gather at a short distance in a cluster, often hanging from a branch or another structure. In September 2017, two researchers observed a swarm attached beneath a concrete table, surrounded by moving scout bees searching for a new site to colonize. Upon returning from their exploratory flights, the scouts brought back information about the location intended to permanently accommodate the swarm. After three days of observation, during which the scouts’ dances appeared to gradually diminish, the researchers were surprised to notice that they were not the only ones waiting.

At the edge of the first layer of bees in direct contact with the table, they noticed a number of pseudoscorpions emerging. They appeared restless and hungry as they moved away from the bee cluster, using their pincers covered with fine, relatively long hairs to detect food in the cracks and roughness of the underside of the table.

The arthropods did not move very far away, as some bees encouraged their return close to them. Very clear communication between the two species was observed, with constant contact: the pseudoscorpions using their pincers in undulating movements or clinging to the bees, and the bees using their antennae and legs to probe and guide the pseudoscorpions back toward the cluster.

This interaction suggests that the presence of pseudoscorpions played an important role for the bees. As activity and communication within the swarm intensified before the flight to its final destination, the bees closely monitored their traveling companions. When the colony eventually took off for its new nesting site, remarkably no pseudoscorpion was left behind.

These observations appear to demonstrate an extraordinary interdependence between bees and pseudoscorpions and suggest that a swarm has a nearly vital need to carry with it some of the pseudoscorpions present in the hive.

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