

SCREW WORM 321 



pensive and easily applied, and those who have worked with it 

 claim that its effects will last for four or five days. If the animals 

 are enclosed and a knapsack sprayer used, a large number of 

 cattle may be treated in an hour. The emulsion is made as fol- 

 lows : Dissolve one-half pound of common hard soap in one gallon 

 of boiling water; add gradually two gallons of fish oil; churn the 

 liquid through a force pump for several minutes; when wanted 

 for use, dilute by adding fifteen or twenty parts of water to one 

 part of stock solution. The United States Department of Agri- 

 culture has recommended tar, or the following mixture: Sulfur, 

 four ounces; spirits of tar, one gill; whale oil, one quart; one appli- 

 cation each week. 



Naturally, housed animals are not so subject to attack, and if 

 animals hi pasture can 

 resort to a shed, to deep 

 shade, or to water, they 

 are much less troubled 

 than those not so pro- 

 tected. Those in charge 

 of milch cows or other 

 cattle kept in barns should 

 be on the lookout at the 

 proper time for bots 



among them Or eggS On FIG. 32 6. Method of squeezing out "grub" or hot. 

 . TTT , (Courtesy of Country Gentleman.) 



the hairs. When seen, 



prompt measures should be used. Cooperation is absolutely 

 essential, in this as in other farm practices against insects, to 

 insure the best results. 



The Screw Worm. This is one of the most injurious of the 

 flesh flies (Chrysomyia macellaria Fab.). It is bright metallic 

 green, with prominent, dull-red eyes, and is a little larger than the 

 house-fly. The back is marked with three distinct black stripes 

 running from head to abdomen (Fig. 327). The larva or maggot 

 is similar to other maggots, but has a ring of bristles between 

 each pair of segments, from which it obtains the name of screw 

 worm. These bristles act as legs hi locomotion. The mature 

 maggot is three-fourths to one inch long, and the mouth parts 

 are represented by two pointed black hooks. 



Life History. The adult female lays an enormous number of * 



eggs on or near dead animals or in open sores of living animals. 

 These eggs hatch in from one to two days, and the maggot attains 

 21 



