CACTUS-FEEDING INSECTS AND MITES 59 



emergence. For instance, of the total eggs from 37 females, 57 percent 

 was J aid on these two nights, the proportion for each evening being: 



Both at Tucuman, Argentina, and at Sherwood, Queensland, 

 moths emerged and laid eggs in every month of the year. Moderately 

 low night temperatures, falling below 50° F., do not discourage or 

 inhibit oviposition, as they do for such cactus phycitids as Cactoblastis 

 cactorum and Melitara prodenialis. The following resiolts were obtained 

 at Sherwood, the given temperatures having been taken in the room 

 where the moths were ovipositing: 



Atonth 

 June 



July 



August 



Moths placed in mason jars or other types of glass containers ovi- 

 posited freely on the loose threads of frayed pieces of cloth suspended 

 in the jars. As the eggs are small and rather delicate, and cannot 

 be handled as readily as can the eggsticks of Cactoblastis and Melitara^ 

 this method of securing oviposition simplified the problem of estab- 

 lishment. The pieces of cloth containing the eggs were placed on the 

 prickly pear in the breeding cages or in the field, and the hatching 

 larvae promptly entered the segments of the plant. 



The incubation period during the six summer months, October- 

 March, normally occupies 7 to 12 days; the shortest period in our 

 records has been 5 days both in Australia and Argentina. The max- 

 imum known duration has been 49 days in the winter months of 

 June-July and July-August. 



Development of the larvae is irregular, and there may be very 

 considerable variation in the time factor among material hatching 

 on the same day. The shortest larval period has been 27 days in 

 Australia and 28-30 days in Argentina. On the other hand, larvae 

 hatching from February to May may not pupate until September and 

 October, a period of 7 to 8 months. 



