334 ^ YEAR OF COSTA RICAN NATURAL HISTORY 



And at the most critical moment of one attempt we had to 

 drive away the steers living in the potrero, for their over- 

 mastering curiosity almost caused them to upset the 

 camera. 



This little ravine contained many groups of a huge un- 

 identified aroid, called by the Costa Ricans "hoja de pato" 

 (goose leaf). It is not peculiar to Alajuela, being found in 

 many places over the Atlantic slope as well as the Pacific. 

 The triangular leaves reach a breadth of nearly two feet and 

 a length of two to three feet, while the leafstalk may be 

 nearly four feet long. One that we measured was over six 

 feet long in a straight line from base of stalk to tip of leaf, 

 but in its natural position the leaf and stalk are at right 

 angles. The rhizome, creeping over the ground or sub- 

 merged in the mud, is six to eight inches in diameter. 



On September eighth we found in lanes between jocote 

 hedges, a number of clicking butterflies mentioned on page 

 296. There were two species, Ageronia ferentina with the 

 hind wings whitish below and Peridromia fornax with the 

 same surface brownish-yellow. They seemed to prefer to 

 alight on bare or nearly bare tree-trunks with the wings 

 outspread instead of folded together as in most butterflies. 

 The flight also is characteristic — a number of quick flaps of 

 the wings, then they are held still while the insect sails for a 

 short distance, after which the rapid flapping is resumed. 

 We caught a few specimens and took them alive to our 

 screened room, where we released them in the hope of learn- 

 ing how the clicking was produced; but during the three 

 days the insects were under observation we did not hear 

 them click. Hampson ^ thinks that in Ageronia arethusa 

 the sound is produced by a pair of hooks attached to the 

 base of the fore wing playing against a pair of hooks on the 

 side of the thorax. I have been unable to find these hooks 



^ Proc. Zool. Soc, London, 1892, p. 191, fig. 3. 



