75 



The habits and life histories of several species have been closely studied 

 by many entomologists during the last twenty years, so that we know the 

 conditions under which we have to work against them. Under ordinary 

 conditions an immense number of eggs never hatch out through want of 

 heat in the early part of winter, and the action of the fly in ovipositing 

 only causes a dull coloured-spot to appear on the skin of the orange, the 

 *' sting mark " of the orchardist. In the maggot stage many get exposed and 

 killed, and there must be also a very large percentage of perfect flies that 

 after they emerge from the pupae cases never reach the surface. We know 

 that in the dry hot seasons fruit-flies are always worse, while after a very wet 

 winter they are never so plentiful. The obvious reason is, that when the 

 orchard soil is sodden and beaten down by rain storms it becomes so hard 

 and caked that any flies from deeply -buried pupae have a very small chance 

 of getting through to the surface. 



In all countries where irrigation is carried out in a systematic manner 

 nnd the ground flooded in basins round the trees at regular intervals, though 

 the fruit-fly is a well known pest, it comes and goes, and is not constantly in. 

 evidence as in Australia and Africa, where conditions are so different. In 

 southern Spain and Sicily this is one of the great factors in the checks upon 

 the increase of fruit-flies. 



Among all the pests that have turned their attention to cultivated fruit 

 there is no group so well protected from natural enemies as the fruit-flies. 

 From the time they emerge from the eggs to the time they burrow beneath 

 the fruit into the soil they are feeding and working beyond the reach 

 of many parasites, predaceous insects, and birds that would otherwise 

 feed upon them. Free to a great extent from enemies that reduce the 

 number of other insects, they are also sa f e from all sprays and contact 

 poisons while doing the damage ; sprays will not kill them, and fumigation 

 with gas, so deadly to scale insects, will not affect them. We have, there- 

 fore, to resort to different methods in dealing with them. We must either 

 destroy, drive away, or capture the perfect flies before they can lay their 

 eggs, or else destroy the infested fruit containing the eggs and maggots. In 

 every country where action has been taken by the Government to protect 

 the gardener and orchardist against himself or his careless neighbours, this 

 has been recognised, and Fruit-fly Destruction Acts have come into force, in 

 which the main principle has been the inspection of orchards, and the 

 compulsory cleaning-up and destruction of all infested fruit. In Mexico the 

 Department of Fomento obtained a grant of money to be expended in the 

 fruit-fly infested orange orchards of Morelo*. The Commission of Parasi- 

 tologia Agricola, in whose hands the work was placed, formulated the 

 following rules : 



(1) Gather each day all mangoes, lemons, and oranges which may have 



fallen from the trees, and deposit them in a clean corner of the 

 orchard. 



(2) Destroy all fruit so accumulated at least once a-week. 



(3) It is preferable to destroy the fruit by burning, but it may be 



disposed of by burial, and when buried it should be covered with 

 at least fifty centimetres (about 20 inches) of soil. 



(4) If the same worm exists in the guava, this fruit should also ba 



destroyed in the same manner. 



I have described in my second Progress Report how I saw this work 

 carried out in Mexico by the inspectors at Yutapec. 



