86 CEREAL AND FORAGE INSECTS. 



ATTRACTION TO LIGHTS. 



Under certain conditions, arising possibly from the amount of 

 moisture in the air caused by distant or passing showers, the male 

 Hemileuca moths are attracted to light during their nocturnal flights. 

 At times these moths will swarm on the window screens and then per- 

 haps not one will appear for a week. In the village of Cimarron, one 

 of the famous stations on the old Santa Fe Trail, the numbers of 

 these insects that gathered on screen doors and at lighted windows 

 were extremely annoying. But this swarming occurred only two 

 or three times during the six weeks of the flight of the species. 



When attracted to a lighted window at night the moths remain 

 there, if undisturbed, until the regular hour for the next day's flight, 

 when they rouse themselves and take to wing as usual. The moths 

 confined within a room grow restive and fly just before sunset, their 

 instinct informing them of the arrival of the time to move. 



FLIGHT DURING STORMS. 



Moths of both sexes often fly during a downpour of rain, more 

 especially the males. Even cold fails to check their flight, and num- 

 bers have been seen actively darting about when the mercury was 

 close to freezing point. In one or two instances they have been seen 

 flying during a snow storm. 



Continued cold, however, is fatal to them. In October, 1908, after 

 a series of snow squalls, when the ground had been white for a day 

 or two, hundreds of dead males were lying scattered about the pastures. 

 In several cases noticed, as many as 25 or 30 males lay dead about a 

 single plant of snakeweed (Gutierrezia sp.) where they had taken 

 refuge from the storm. 



Dead females are much less frequently seen, though they some- 

 times perish with cold while endeavoring to oviposit. 



COLOR AS AFFECTED BY CHANGES IN TEMPERATURE. 



Great and unusual changes in temperature during the pupal stage 

 appear to affect to some extent the colors of the adult. October 20 

 and 21, 1908, a fall of snow on the infested range was followed by a 

 temperature several degrees below freezing point. The emergence of 

 the moths was at its height when the snow came, but was almost 

 wholly checked for several days by the cold. When the weather 

 again became warm and fresh moths appeared, they were noticeably 

 lighter in color and with much less definite markings than those that 

 had emerged previously. After a few days of warm weather, the 

 moths as they emerged possessed their normal colors and markings. 



