BIRDS OF PORTO RICO. 9 



Only one lizard, the siguana (Amelva exul) , an important terrestrial 

 form, is disappearing. Few of these, however, are eaten by birds, so 

 that their diminution is to be charged to other agencies, perhaps to 

 the mongoose, as this lizard can not climb. Many spiders also are 

 eaten, more especially in the dry localities where they abound. 



The value of the birds studied here is necessarily ascertained 

 largely through a consideration of their insect food, certain domi- 

 nant insect forms being so destructive that their bird enemies are of 

 the utmost importance. The economic status of many insects com- 

 mon in Porto Kico is at present uncertain, and as they are more 

 thoroughly studied some will undoubtedly prove very destructive; 

 the lists of insects identified, as contained in the body of this report, 

 will then serve as an index to their bird enemies so far as at present 

 known. It is unfortunate that a robust bird like the pearly-eyed 

 thrasher {Mar gar ops f. fuscatus) should devote its attention to wild 

 fruits instead of to insects, but the conditions favor frugivorous 

 species. 



With these brief general statements, we pass to a consideration of 

 the bird enemies of a few of the well-known insect pests. 



BIKD ENEMIES OF THE MOLE CRICKET. 



The changa, or mole cricket (Scapteriscus didactylus), is without 

 doubt the best-known insect in Porto Rico, as it is among the most 

 injurious. Though found in other parts of the West Indies, in 

 South America, and in southern United States, its ravages reach 

 their maximum in the region under consideration. Living almost 

 entirely in the ground, it escapes attention for the most part, and the 

 adult, with its strong fossorial front legs and chitinous thorax, is 

 too large and tough a morsel for many birds. The nymphs, small 

 images of their parents, and varying in size with age, are more at- 

 tractive to the average bird. At plowing time many are exposed to 

 the watchful eyes of their enemies, and others, forced near the surface 

 in the lowlands by water in the soil, are unceremoniously haled forth 

 and swallowed. The blackbird (HoloqaiscaZus brackypterus), popu- 

 larly considered one of the greatest enemies of " la changa," in reality 

 destroys but few, though it sustains its reputation as a beneficial 

 species in other ways, as will presently be seen. Other species, how- 

 ever, make up for the blackbird's shortcomings, and among them the 

 despised martinete (Butorides v. cubanus), ridiculed for its ungain- 

 liness, ranks foremost. Standing watchfully, with head drawn in, 

 among the short growth of the young cane fields, or walking with 

 lengthened stride along the border of lowland pools, it spies and 

 avidly swallows both adults and young of the mole cricket. The 

 species at present known to aid in suppressing this pest number 21. 



