OF WASHINGTON. 165 



foliated by the attacks of a caterpillar. Large trees which had 

 been bearing crops for a number of years stood without a 

 particle of foliage, their bare petioles and midribs resembling 

 skeletons and with none of the ragged picturesqueness charac- 

 teristic of this species. Some of the trees were in hopeless 

 condition and had to be cut down, but the rest recovered 

 under special care given them. 



Later in the same year, about the middle of September, the 

 caterpillars again appeared, although not in the same large 

 numbers as before, and began to strip the trees anew. All 

 cocoanut trees were, therefore, sprayed with a weak solution 

 of arsenate of lead, a most tedious and troublesome, although 

 very effective, method of combating these insects, in view of 

 the great height of the trees, most of which measured from 30 

 to 35 feet. This time some of the royal palms were also, but 

 not very badly, affected, and in their case spraying was out of 

 the question, their still greater height making it impossible to 

 reach them by ladders ; and " royals," particularly the Oreo- 

 do.va oleracea, have too thick a trunk to allow even the natives 

 to climb them. 



Although the torrential rains washed off the arsenate of 

 lead after a few weeks, it stayed on long enough to kill all the 

 insects on the trees which had received treatment, but a num- 

 ber evidently reached maturity on the royal palms and de- 

 posited their eggs in turn on the cocoanut trees. 



This year ( 1907) the caterpillars made their first appear- 

 ance in May, during my absence from Ancon through vaca- 

 tion, and I found a number of trees sporadically infested with 

 them on my return. I suppose this was the time when the 

 mature insects deposited their eggs freely on all cocoanut trees 

 in this vicinity, for about the latter part of August thousands 

 of their larvae began to defoliate these palms again, evidently 

 determined not to leave a single leaf on the trees. 



One thing in their favor is the circumstance that the larvae 

 feed only at night and that they retire before the first sun-rays 

 into a tough web spun with pinnae of the leaves, where fre- 

 quently as many as 700 to 800 of them crowd together into one 

 " nest." The lower part of this, where the ends of the pinnae 

 meet, is left slightly open, probably through instinct of the 

 caterpillars, to allow for the escape of their dung, and the 

 whole presents the appearance of a long narrow bag, from 30 to 

 60 centimeters in length, according to the number of insects it 

 contains. Frequently a tree will have two, three, and even four 

 of these " nests " and some were found with an estimated 

 number of over two thousand full-grown larvae. What even 



