DIPTERA. 89 



from the larva to the pupa. It has thus taken the Dacus twenty-seven 

 to twenty-eight days to arrive at this state, from the time the egg was 

 laid ; besides which, this species, in the warm climates of Provence 

 and Italy, can reproduce itself several times from the beginning 

 of July, the period at which the first flies begin to lay, till the end 

 of autumn. 



In order to save a considerable portion of the olive crop of these 

 countries, M. Guerin-Meneville has advised hastening the harvest 

 sufficiently for all the olives to be pressed at a time when the larvae of 

 the last generation, which would be preserved in the olives that are 

 left, or in the earth, according to the climate, are still in the fruit. 

 If a first operation were not sufficient to destroy them all, it should 

 be repeated the following year. The sacrifice entailed by this 

 practice would be amply compensated by a succession of good crops 

 and the certainty of a sure and permanent profit. In fact, by an 

 early gathering at least half a crop of oil is still obtained ; whereas, 

 by waiting for the usual period of gathering the olives, sufficient time 

 is left for the larvae of the Dacus to devour their parenchyma, which 

 deprives them of the little oil that they might have yielded if their 

 destruction had been accomplished earlier. This early gathering has 

 the advantage of causing the destruction of a great number of larvae, 

 which will be so much towards diminishing the means of reproduction 

 of the fly. 



