Tropical Liaisons on a Beetle's 



In the rainforests of Central and South America, pseudoscorpions and harlequin 

 beetles are more than fellow travelers 



by Jeanne A. Zeh and David W. Zeh 



The forest of Panama's Soberania Na- 

 tional Park felt almost cool after a torren- 

 tial afternoon downpour. It was early May 

 1988, and the wet season had just arrived. 

 The forest, parched after four months 

 without rain, was springing back to life. 

 Near dusk, a shaft of pale light still pene- 

 trated the dense canopy. After a long day, 

 we were tired, drenched, and mud spat- 

 tered. We took a compass reading and 

 headed back toward a trail. Suddenly, we 

 spotted what we had been searching for. 

 Lying amidst the tangled green wreckage 

 of a newly opened forest gap was the trunk 

 of a huge, fallen fig tree. Struggling 

 through the chaos of twisted Uanas and 

 splintered black palms, we hacked a path 

 to the tree. Pungent, milky sap still oozed 

 from the fig's broken limbs. We could 

 hardly beUeve our luck at finding a fig tree 

 that must have fallen only a day or two be- 

 fore. We had previously come across a few 

 fallen fig trees, but they had all been well 

 along in the decay process. 



A recently fallen fig, we knew, was sure 

 to attract the most sfiiking of all the long- 

 homed beetles, the harlequin, named for 

 the pattern of swirling crimson, black, and 

 greenish yellow that decorates its body. As 

 arachnologists, our main interest was not 

 in this magnificent beetle itself, but in its 

 tiny passengers, pseudoscorpions belong- 

 ing to the species Cordylochemes scorpi- 

 oides. The false scorpions lack a tail 

 tipped with poisonous stingers, but they 

 can immobilize prey with poison pro- 

 duced by a gland in their pincers. If you 

 were to prize open a harlequin's wing cov- 

 ers, you would almost certainly find at 

 least one pseudoscorpion, maybe more. 

 The record stands at fifty-four, all cUnging 

 tenaciously to the abdomen of a single, 

 large male beetle. Naturalists have been 

 aware of this curious association ever 

 since Linnaeus described it in 1758, but 

 why the pseudoscorpions engage in this 

 beetle-riding behavior has been a mystery. 

 Do they climb on board to feed on the 

 mites that infest the beetles? Do they 

 spend their entire lives on the beedes? Or 

 are they simply catching a ride, with the 

 harlequins providing jumbo jet service be- 



36 Natural History 3/94 



