Nov. 5, 1921 Pale Western Cutworm 305 



MOTHS BOTH NOCTURNAL/ AND DIURNAL 



During the last half of August when the nights were warm and night 

 flying was at its height the moths remained inactive during the day, 

 hiding under clods and weeds. As the nights grew colder, the moths 

 flew only an hour or two after dark, and on September i they were seen 

 flying during the day. On this date they began flying about 4.30 p. m. 

 and were seen in abundance feeding upon sunflowers, golden rod, 

 tumbling mustard, yellow greasewood and lamb's quarter. All but one 

 of the moths seen at flowers at this time were males, a search under 

 weeds and clods at the same time revealing only females. At 8 p. m. 

 when the flower patches were visited moths were still feeding in large 

 numbers, practically all of them being females. They paid no attention 

 to lights, and none were caught in a trap light set close by. As the night 

 grew colder all of the moths disappeared and could be found hiding under 

 clods or weeds. On the following day moths were found feeding at 

 flowers at i p. m., and at 3.30 p. m. a patch of yellow greasewood 

 {Chrysanthus jrigidus), which seemed to be the favorite flower, had 

 attracted dozens of Porosagrotis orthogonia, nearly all of which were 

 males. At 5.30 p. m. the patch was again visited, and it was found that 

 the males were then leaving and that females were flying to the flowers 

 from a nearby summer-fallowed field. On September 3 moths of various 

 species were found feeding during the morning, and at noon the flowers 

 of the yellow greasewood were covered with moths, none of which were 

 P. orthogonia. At 3 p. m. about 10 per cent of the moths present at 

 flowers were P. orthogonia. These gradually increased in numbers until 

 6.15 p. m., at which time practically all other species had disappeared. 

 After the moths had finished feeding they invariably flew toward the 

 higher ridges and knolls in neighboring cultivated fields. Many of the 

 moths in coming to the flowers were seen to fly from 200 to 500 yards 

 directly against a stiff breeze. Moths were seen flying to flowers in large 

 numbers until September 8, when a cold rain and wind occurred. The 

 males were always found feeding earlier in the day and the females later, 

 although neither was ever found before noon. 



ECONOMIC IMPORTANCE 



The record of this cutworm during the last 10 years has demonstrated 

 its capacity for doing enormous damage to grain crops. When in 191 1 

 Porosagrotis orthogonia, then an obscure insect, suddenly increased in 

 numbers and did considerable damage to grain in southern Alberta {10, p. 

 iji) little importance was attached to it. In the following year, however, 

 when 33 per cent of all the grain sown in the Lethbridge land district 

 was destroyed and an accurate estimate by the superintendent of the 

 experiment station at Lethbridge placed the actual loss from this insect 

 at from 30,000 to 35,000 acres (jj, p. 506) it was looked upon as a pest of 



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