ANNUAL REPORT, 1935 49 



1981 1935 



Total insects caught 42,857 89,702 



Injurious insects 1,037 3,042 



Eeneficial insects 1,489 826 



Codling moth 321 83 



Apple tent caterpillar moths 584 1,355 



Forest tent caterpillar moths 52 280 



Among the other pest insects which were found in the traps during 1935 

 but not in 1934 were: the common stalk borer, the armyworm, the satin moth, 

 and the northern corn root worm. 



Records of the daily catches when compared with the weather conditions 

 show that while rain reduces the number of insects caught during the night of 

 a storm, a peak occurs on the following night. For instance, the heavy rain of 

 July 7 and 8 caused a comparatively small catch for the two nights (1394 and 

 554), but on the following night, July 9, a marked peak occurred (3,984) and 

 was the largest night's catch for the season even though the temperature was 

 only 72° at 8:30 p. m. 



Temperature is the most important single weather factor in governing insect 

 catch in light traps. In the majority of cases a peak in temperature was 

 accompanied by a corresponding peak in the number of insects caught. How- 

 ever, when making such comparisons it must be remembered that a large 

 number of insects with widely varying habits and life histories are being con- 

 sidered and all these insects probably are not influenced in the same way by 

 weather conditions. 



Beneficial insects comprised but 0.9 percent of the total number of insects 

 caught as compared with 3.7 percent in 1934. Peaks of emergence concurring 

 with peaks of temperature agree with the theory advanced in last year's work, 

 that temperature has a greater effect upon parasite emergence than on Lepi- 

 dopterous insects. 



In determining the relative efficiency of the various colors of the lights used 

 in the traps, allowance had to be made for the location of the traps, which was 

 an important factor in governing the numbers of insects caught. The traps 

 on the ends of the rows caught nearly twice as many insects as those between 

 them. Collections show that the colors of high frequency (blue and green) 

 are superior to those of low frequency (amber and red. ) The total collections 

 show that the blue light attracted the greatest number of insects; the green, 

 second; the amber, third; and the red, the least. In comparison white light 

 was shown to be less satisfactory than the colored, particularly those of high 

 frequency (blue). 



Of the insects caught, among the Diptera the families Tipulidae, Culicidae, 

 Bibionidae were most strongly attracted to blue light. Drosophilidae were 

 very strongly attracted to amber light. Among the Lepidoptera but little 

 preference was shown. The Noctuid moths (adults of cutworms) were 

 attracted chiefly to red light and least to blue; while the Pyralidae were 

 strongly attracted to blue and less to amber, green or red light. One species, 

 the codling moth, showed a preference for high frequency colors, notably blue. 



The experimental work of 1935 again emphasized the fact that light traps 

 furnish a very accurate index of the emergence rates of insect species and also 

 of their relative numbers from year to year. It was also apparent that insect 

 species show a marked color preference and that for the most part this preference 

 is for the high frequency colors. 



