Beneath the open wing covers of a harlequin beetle, below, two 

 closely matched male pseudoscorpions are locked in battle. 

 More than a dozen pseudoscorpions. right, hitch a ride on a 

 small male harlequin that has just emerged from its pupal 

 chamber in a rotting fig tree. When the beetle takes flight to 

 search for another tree, it will transport the false scorpions and 

 a number of much smaller mites. 



Photographs by Jeanne A. Zeh 



converge on adult beetles. Equipped only 

 with a pair of poorly developed eyespots, 

 the pseudoscorpions unerringly head 

 straight for the "boarding gate," the rear 

 end of a beetle's abdomen. One by one, 

 males and females raise their claws, pinch 

 the beetle's rear, and as the harlequin re- 

 acts by flinching its abdomen, the pseu- 

 doscorpions quickly clamber on board. 



Heavily laden with the stowaways, the 

 harlequin climbs to the highest available 

 point on die trunk and launches itself into 

 the air in search of another fig tree on 

 which to mate. 



We have found that the female harle- 

 quins are extremely fastidious in their 

 choice of trees. Our survey of a 150-acre 

 tract of forest showed that 80 percent of 

 the beetles we located were on newly 

 fallen trees. Depending on their size, the 

 trees attracted adult harlequins for only a 

 brief period of from four to twenty-six 

 days. We found the remaining 20 percent 

 of the beetles on standing dead trees. 



While a harlequin flies in search of a 

 fallen tree, the pseudoscorpions must 

 avoid falling off the vertically held ab- 

 domen of their host. Instead of simply 

 clinging to the segments of the beetle's ab- 

 domen, they attach themselves with a 

 safety harness of silk, produced by a gland 



in their pincers. When the harlequin finds 

 a suitable fig tree, the pseudoscorpions use 

 silk again. They cannot fly or jump, but, 

 undaunted, they spin a silken thread and 

 rappel down to their new habitat. 



Our field observations confirmed that 

 the pseudoscorpions use the beeties to dis- 

 perse from old, exhausted trees to newly 

 fallen ones, hi examining more than 150 

 beetles, we have found only adult pseu- 

 doscorpions. Because mature pseudoscor- 

 pions are voracious and opportunistic 

 predators not averse to cannibalism, the 

 crowded beetle abdomens are no place for 

 the weak and vulnerable. (We have often 

 seen adults in trees feeding on nymphs, as 

 well as older nymphs feeding on younger 

 ones.) What was unexpected was the large 

 number of beetles carrying just one pseu- 

 doscorpion, always a male. Of the fifty- 

 eight harlequins we examined on recently 

 fallen trees, fifty-three were occupied by 

 lone males. Their pincers, used for fight- 

 ing, were markedly larger than those of the 

 average males collected from the trees. 

 These big males remained on board even 

 when their host beetles stayed on the trees 

 for several days. 



To investigate this perplexing finding, 

 we marked 136 virgin male and female 

 pseudoscorpions and allowed them to 



mount beetles in the laboratory. Then we 

 released the harlequins on a newly fallen 

 fig tree. Recapturing the beetles a few 

 hours later, we identified the remaining 

 pseudoscorpions and found that the fe- 

 males and small males had disembarked 

 rapidly, but the bigger males had stayed 

 aboard. Only when there were no females 

 aboard did large male pseudoscorpions 

 show any inclination to abandon their 

 hosts, and in such cases they often simply 

 transferred to another beetle. In a few 

 cases, we recaptured marked beetles for a 

 second and a third census. On one, a male 

 pseudoscorpion was still present after 

 fourteen days, and in the interim, two fe- 

 males had come aboard. Because female 

 pseudoscorpions disembark rapidly, we 

 were only able to recapture ten on flieir 

 original beetles. Of these originally virgin 

 females, eight subsequently produced 

 brood sacs and nymphs in the lab, indicat- 



40 Natural History 3/94 



