THE PRICKLY PEAR. ] 445 



extensive or so acute as to constitute a danger. Attacks 

 of gangrene due to a species of bacterium sometimes 

 develop in autumn in the wounds caused by hailstones, 

 and whole branches may rot off as a result of this disease, 

 particularly if its development is favoured by a spell of 

 moist and sultry weather. The scale insect Aspidiofus 

 Hederae Val. is common on prickly pears, but never 

 causes serious trouble. The fruit fly Ceratitis capitata 

 Wied. punctures the fruit in August and September, 

 and too often a considerable proportion of the crop is 

 destroyed by this pest. 



