PARASITIC DISEASES OF CATTLE IN PUERTO RICO 25 
fly is unimportant in cattle in comparison with the hornfly, but in 
the other areas, at times, it is as common and serious as the hornfly. 
The treatment is the same as for the hornfly (p. 22). All decaying 
vegetable material around the stables should be cleaned up every 
few days and placed with the manure in fly-tight bins or pits. 
Mosquitoes. — Various species of mosquitoes attack animals, espe- 
cially horses and cattle. The actual damage caused by them is not 
known, but it may be considerable where mosquitoes are numerous. 
Investigators connected with the Bureau of Malaria Control of 
Puerto Rico have found by actual count that the two species of 
mosquitoes transmitting malaria show rather a decided preference 
for feeding upon horses and cattle as compared with man. No 
practical method has been found for protecting livestock from 
mosquitoes. Destroying the breeding places by drainage or treat- 
ment with oil or paris green or by impounding water and using cer- 
tain species of small fish which eat the wrigglers or larvae are always 
important control measures for mosquitoes. 
Fleas. — Occasionally fleas attack young stock which are confined, 
in sufficient numbers to cause considerable irritation and a loss in 
condition. These pests can be controlled by spraying with kerosene 
or with the kerosene-pyrethrum extract sprays. First cleaning up 
the litter and then spraying the floors and walls of the stable with 
kerosene are also important control measures. 
The leeches or " sangruijuelas." — The leeches (fig. 2, J) should be 
mentioned as occasional parasites of some importance. They are 
very abundant in swampy land. They attach themselves to any 
part of the body of the host animal which they can reach, while the 
animal is standing in water, and occasionally enter the mouth or 
nostril while the animal is drinking. 
Leeches not only suck considerable blood, increasing enormously 
in size, but make wounds from which there is some hemorrhage after 
the engorged leeches become detached. Leeches can be destroyed 
by treating the water with copper sulphate, as described for the 
snail transmitting the liver fluke. 
Poisonous arthropods. — According to the unpublished statement 
of one authority, 4 there are a number of arthropods reputed to be 
poisonous, among which may be mentioned the so-called tarantulas 
of the family Avicuiaridae ; large centipedes; several species of 
-scorpions; and at least one species of whip scorpion known locally 
as the " guava." The " guavii " is probably the most dangerous of 
the group. Owing to lack of scientific investigations it is impossible 
to make any definite statements as to the exact degree of their ven- 
omous qualities. However, there is little or no direct evidence that 
the poisonous arthropods in Puerto Rico, except for occasional and 
unimportant injuries, are dangerous to cattle or other animals. 
Exotic parasites. — Both external and internal parasites have been 
found in imported cattle. Among these, the cattle grubs. Hypo- 
derma spp., the larvae of warble flies, are common and conspicuous. 
Small tumors or lumps are found in the skin of the back, which con- 
tain the larvae (fig. 2, G). There is no authentic record of these flies 
having reproduced themselves in this climate. 
* Stuart Danforth, professor of zoology, University of Puerto Rico. 
