166 THE SENSE ORGANS AND REFLEX BEHAVIOUR 



moths from adjoining fields and thus intensified the attack in the 

 area concerned. 



The use of Hght traps for the destruction of injurious Coleoptera 

 has been principally applied against members of the Scaraba^idse, 

 more especially the genus Lachnosterna. Sanders and Fracker 

 (1916) record the great attraction artificial light has for various 

 species of this genus. During May and June, 1914, 440,000 

 examples were captured by this means in a single locality, while 

 forty light traps in five localities captured 1,036,400 of the beetles. 

 The males caught greatly exceeded the females in number, but in 

 some of the commoner species females formed a larger proportion 

 earlier in the season. In Porto Rico, Van Zwaluwenburg records 

 the attraction of large numbers of Lachnosterna to light, the 

 sexes responding in about equal numbers, and he estimates that 

 only about 17 per cent, of the females had completed oviposition 

 at the time of capture. 



An investigation of the activity and frequency of insects based 

 upon those caught in light traps has been carried out for several 

 years by WilUams (1935, 1936) at the Rothamsted Experimental 

 Station. In the analysis of the figures obtained it was demon- 

 strated that, taking all insects together, the maximum number was 

 trapped at the beginning of the night with a steady decline towards 

 the morning. The Diptera, which composed about 76 per cent, 

 of the total, showed a maximum in the first part of the night and 

 the Lepidoptera, which formed 16 per cent, of the total, were 

 caught in largest numbers in the second to fourth periods — the 

 night being subdivided into eight periods of equal length. When 

 there is a marked difference in respect to the number of individuals 

 of each sex, the females appeared earlier in the light trap than the 

 males. The total captures of insects in two successive years 

 exceeded 100,000 specimens per year, so the numbers appear to 

 be sufficient to warrant the deductions drawn. An examination 

 of the insects captured during three successive years was made in 

 order to test the validity of the general belief that the nocturnal 

 activity of certain kinds of insects is reduced at full moon. The 

 analysis had special reference to the Noctuidae, and it was 

 considered that the lunar effect on the captures at a light trap 



