MONTANA INSECT PESTS, 1949 AND 1950 29 



the state are readily controlled by locating the nests and spraying 

 that general area with 5% chlordane. 



FLIES (Muscidae Family) 



Resistance of houseflies to chlorinated hydrocarbon insecti- 

 cides has received considerable attention over the United States 

 during the past several years. It appears that this condition is 

 also occurring in Montana. This is substantiated by several cases 

 reported by custom pest control operators. Houseflies have appar- 

 ently become resistant in one case to DDT and in another to 

 lindane after two or more years of successive use of these insecti- 

 cides. This clearly indicates the need of frequently changing 

 insecticides when they are used consistently in one area. 



INSECTS DESTRUCTIVE OF MAN AND ANIMALS 

 MOSQUITOES (Culicidae Family) 



In general, conditions were more favorable to mosquito de- 

 velopment m 1950 than they were in 1949. In certain areas of 

 Montana, particularly the Milk River Valley, mosquitoes repre- 

 sented a serious hazard to the livestock industry, as well as an 

 important nuisance to man. Recent work conducted by the Mon- 

 tana Agricultural Experiment Station on mosquito population 

 sources and practical control measures will probably pave the way 

 to economical, more practical, area-wide mosquito control pro- 

 grams in Montana in the future. 



CATTLE GRUBS (Hypoderma lineatum and Hypoderma hovis) 



There were no noticeable changes in the severity in cattle 

 grub infestations during the past two years as compared with 

 previous years that cattle grubs were studied and observed. It 

 has become apparent through intensive research studies conducted 

 by the Montana Agricultural Experiment Station and observations 

 in the field that the present methods of cattle grub control prac- 

 tised by stockmen on beef cattle in Montana fall far short of 

 providing economic returns in terms of grub reductions and pro- 

 tection of cattle from these insect parasites. 



CATTLE LICE (Anoplura and Mallophaga Orders) 



Three species of cattle lice are commonly found on Montana 

 cattle. Two of these are sucking lice, Haematopinus eurysternus 

 and Linognathus vituli, while the third is a biting louse, Bovicola 

 hovis. All cattle inspected during the winter and early spring 

 have been found to be infested in varying degrees, indicating 

 that this 13 a general condition. Infestations of cattle lice are 

 generally found to be more severe during particularly hard win- 

 ters; consequently, severe cattle louse infestations generally oc- 

 curred during the hard winters of 1948 and 1949. 



