TWENTY-NINTH REPORT OF THE STATE ENTOMOLOGIST 15 



tick feeding, needle grass, dehorning, castration, branding, etc., 

 and they may also attack the navel of newborn calves. Humans 

 are occasionally attacked and there are a number of records of 

 nose or ear infestations in man. 



These flies have a great ability to reproduce. A female may 

 lay approximately 3.000 eggs in batches of from 10 to 400. Three 

 hundred may be laid in from four to six minutes. The eggs hatch 

 in less than a day under usual conditions, and the larvae complete 

 their growth in from three and one-half to four and one-half days. 

 Fully developed larvae (figure 4) drop to the ground where the 

 transformation to the adult takes place. Under the best of condi- 

 tions a complete generation may develop in about 11 days. It 

 is, then, possible for many generations to appear even under Mon- 

 tana conditions, and for very heavy infestations to occur in the 

 host animals. 



The primary screw worm is found throughout the southern 

 states and far into South America. The 1941 Montana records were 

 from Yellowstone and Treasure counties where in August the 

 maggots were taken from the navel of a three weeks-old calf. Ac- 

 cording to information received from the rancher another calf had 

 a severe infestation in a fresh brand and seven out of eight cas- 

 trated calves in one group became infested. The area involved 

 Meyers, Custer, and Big Horn, and included stock belonging to 

 thirteen different ranchers. Forty-four animals were known to 

 have been attacked and several of the ranchers merely listed their 

 stock as being infested, with no numbers of animals given. Cattle, 

 horses, pigs, and dogs suffered injury. 



While this is the first record of the primary screw worm in 

 the State it is entirely possible that this pest has been brought into 

 Montana at other times. As has been previously pointed out, the 

 chances are that it cannot survive the winter here, and our prob- 

 lem is one of continuous introduction. Most of the cases in 1941 

 occurred from the last of July to September 15th. indicating that 

 it took some time for the infestation to develop to a size which was 

 readily noticeable, for the suspected introduction of the maggots 

 dated back to April 18. with the arrival of the Mexican cattle. 



It is important that future shipments of southern cattle into 

 Montana should be thoroughly examined for wounds which might 

 possibly be infested with this insect. Any maggots which may be 

 recovered from such situations should be sent, preferably alive. 

 to the Department of Zoology and Entomology, Montana Agricul- 

 tural Experiment Station. Bozeman. 



spixose ear tick.- This tick (Otiobius megnini Dugesj is pri- 

 marily a southern pest. In the United States it is most common in 

 the southwest, but it has been reported from as far north as Iowa, 

 Alberta, and Oregon. Concerning these ticks in Canada, Hearle 

 says that they "probably were introduced on imported animals 

 and fortunately they do not appear to have become established." 



