The Flight of Nocturnal Lepidoptera 47 



In general, the season was marked l)y the scarcity of cutworm 

 moths. No specimens of Septis arcfica, normally an abundant species, 

 or of any species of Rnxoa were captured. The hot, drv weather of late 

 July and early August materially reduced the numbers of the second 

 broods of the various species, especially Cirphis unipuncta. of which 

 the number caught was less than that of the overwintering brood. 

 It is evident that Agrotis c-nigntm and A. ypsijon are double-brooded 

 in this region. A. c-nigntm was reared during the summer from eggs 

 obtained from a moth caught alive in the traps in June, and the second 

 brood emerged at about the time of the peak of the second brood 

 in the field. The first brood of Carpocapsa poiiioiiclla was not re- 

 corded, and must have been present in verv small numbers. The abun- 

 dance of Balsa )uala>ia is quite unusual. Lugger ( 1 ) records the spe- 

 cies as "rare." The larva lives on apple, but so far as is known, it is 

 not of economic importance here. The bulk of the unidentified Micro- 

 lepidoptera belonged to tw^o or three species of leaf-rollers, but were 

 not separated, as not being of importance in this study. 



II. Meteorological Relations of Minnesota Noctuidae 



In this section it is proposed to treat briefly the influences of the 

 various weather factors on the flight of the larger Noctuids (Group I, 

 Table I ) . It would undoubtedly be better to deal with a single spe- 

 cies, but it is quite evident from Plate VI that all of these species react 

 in a similar manner, and the figures are more reliable, being based on 

 a much larger number of individuals. 



The data on which this treatment is based are given in full in 

 Table II. Many of the traps were used at various times in experi- 

 ments with dififerent baits, so it was thought best to exclude their 

 catches during such periods from this consideration, and treat only 

 those caught on the single bait. During the period from August 4 to 

 August 13, the writer was unable to attend personally to the traps, 

 and the catches were preserved in alcohol. The species could not be 

 determined with any accuracy, so only the total catch is given on 

 Plate VI, and those dates are omitted from this discussion. The catch 

 for July 20 was lost, and is also omitted. 



In order to obtain data which would eliminate as far as possible 

 the variations in catch due to the emergence of species, the follow- 

 ing treatment was resorted to. A "sliding average" or "normal" catch 

 was computed by taking the average of the catches for the first five 

 days, placing this opposite the middle day of the period ; dropping the 



