PARASITOLOGY. 31 
tumors are formed, with holes at their summits. 
The holes become larger as the tumors and larvae 
develop. The larval stage lasts ten months. In 
this stage they are called grubs, or warbles. By 
spring they have developed into full-grown larvae, 
and leave the tumors through the holes in the 
summits. At this time they are three-fourths to 
seven-eighths of an inch long, and nearly one-half 
inch thick. It has been observed that they leave 
behind a tough brown or black skin. They bur- 
row into the ground and pass through the pupal 
stage in from four to six weeks. 
Animal Attacked.—The ox. 
Parts Infested.—Oesophagus and sub-detmal tu- 
mors in region of back. 
Injury to Host.—Some irritation, If attacked by 
large numbers the animal does not thrive. In those 
cattle that are slaughtered during the grubby season 
there is a great commercial loss to hides, on account 
of the holes in the skin. The percentage of cattle 
infested varies from practically none in the northern 
states to seventy-five or eighty percent in the south- 
ern states. 
THE FLEAS. 
PuLEX IRRITANS (Pulex—fiea, irrito—to excite). 
Synonym.—Human flea. 
History—Common in dwellings in Europe. Found 
in the United States, particularly on Pacific coast. 
Description—Body flattened from side to side; 
head small and rounded; stylet arranged for piercing 
the skin and sucking the blood; two eyes and two 
antennae. The abdomen is provided with nine rings. 
