CACTUS-FEEDING INSECTS AND MITES 47 



and the narrow-jointed 0. utkilio and 0. retrorsa at Resistencia in 

 the Argentine Chaco. In the Province of Santiago del Estero, heavy 

 concentrations of larvae have been observed on many occasions in 

 extensive fields of the low-growing, narrow-jointed species 0. utkilio 

 and 0. discolor; areas of the latter species were practically eradicated 

 by this insect, while 0. utkilio suffered very severely. The related 

 0. aurantiaca was heavily attacked in southern Entre Rios. Larvae 

 were located in quantity in the tree pear 0. cordobensis in the northern 

 pai't of the Province of Cordoba. 



Both in Argentina and in Australia there are normally two gen- 

 erations annually, a shorter summer generation with adults emerging 

 in January to March, and a longer winter generation with moths 

 appearing in September to November. In the warmer parts of Queens- 

 land, there is a partial third generation in the autumn, the adults 

 emerging in March to May. Occasional records have been made 

 in the more southern districts of New South Wales where the life 

 cycle occupies 12 months. It is possible, too, that there is one annual 

 generation in southern Uruguay; pupae secured at Piriapolis in 

 December produced moths in late January, which is very late for 

 the normal after-winter emergence and rather early, in view of the 

 cooler climate of the region, for the usual summer generation. 



In Australia, the average length of the life cycle is 100 to 120 days 

 in the summer generation and 235 to 265 days in the winter gen- 

 eration. The shortest life cycle on record was completed in 75 days in 

 midsummer. In the winter generation the eggs are laid in January 

 to March and hatch in February to April. The larvae may develop 

 rather rapidly to reach almost full growth by early winter (June), 

 or grow more steadily to attain full size about the end of July. Pupation 

 starts in August and is general in September. Moth emergence begins 

 in September, reaches a peak in October, and terminates in No- 

 vember. In the summer generation the eggs hatch in November and 

 December, the larvae are full grown in January, and the moths emerge 

 from January to March. The emergence period in any locality oc- 

 cupies about 4 weeks in the summer generation, but most of the 

 moths emerge within 10 to 12 days. In the winter generation emer- 

 gence continues for about 6 weeks, the majority of the moths appearing 

 within a period of 2 to 3 weeks. 



The adult female has a wing expanse of 1}^ to \% inches, the male 

 1}^ to \% inches. The forewings are brown-grey, lighter along the 

 anterior margin, with indefinite wavy transverse markings toward 

 the distal margin; the hindwings are white at base, smoky brown on 

 the outer half, with a dark line along the posterior margin. The fore- 

 wings of the male are rather lighter in shade than those of the female, 



