36 Notes on Insects Damaging Sugar Cane in Queensland. 



throughout their aerial existence, such reaction being governed by 

 various meteorological and other conditions. Flight commences at dusk, 

 but specimens do not enter the traps until 8 p.m. (45 minutes later) 

 when all signs of daylight have disappeared. The table given below 

 records results obtained on three consecutive evenings by a trap specially 

 designed by the writer for this branch of control. 



Total figures represent the result obtained in six hours by a single 

 trap placed among plant cane, and illuminating about one cardinal point 

 of the compass, at a time when the first brood of beetles were emerging. 



It is important to note in this connection that an interval of three 

 weeks elapses between the acts of emergence and oviposition, and that 

 the beetles do not as a rule all leave the ground on the same date. The 

 primary brood usually issues from ploughed land towards the end of 

 November, appearing first in localities where land is of a light character 

 and a week or so after on red volcanic and heavy soils. Finally, an 

 emergence may occur still later from unploughed forest country. Thus 

 it becomes apparent that the individual grower may be called upon to 

 deal with two lots of albohirta arising at different times from cultivated 

 and forest lands, in which case the period preceding oviposition — the 

 only profitable time for using light traps — would necessarily be pro- 

 longed for a month or even six weeks, dating from the first appearance 

 of the beetles. 



Stomach Poisons for the Beetle. 



During February (1915) experiments were instituted to test the 

 insecticidal effect of lead arsenate and other chemicals when applied to 

 favourite food plants. Results may be briefly stated as follows, figures 

 referring to days to be taken in each case as being average numbers: — 

 Arsenate of lead, 2 lb., mill molasses, 1 lb., in 50 gallons of water, proved 

 fatal after nine days to beetles consuming about half a s(iuare inch of 

 poisoned leafage. A similar proportion of arsenate with the addition of 

 1/2 lb. soap killed in ten and a-half days, the latter ingredient seemingly 

 being less palatable than molasses, as although in this case 62 beetles were 

 employed, they consumed only 24 square inches during a longer period. 

 Stronger arsenato-molasses solutions were found less effective, 3-50 and 

 4-50 strengths taking ten days to kill, while the proportion of poisoned 

 leafage devoured by the 52 beetles used amounted to about half that of 

 shoots treated with 2-50-1 molasses formula. 



