﻿324 POMONA COLLEGE JOURNAL OF ENTOMOLOGY 



a depth of one inch and a few an inch and a half below the surface. After 

 three weeks or a month the hy emerges from the pupa and from the ground 

 to commence the work of another generation. 



Unfortunately the life-history has never been worked out in the field 

 by an expert entomologist, so that the above time lengths can not be exact. 

 The department of parasitology in Mexico City has worked it out roughly 

 and found that there are on an average of four generations each year. The 

 generations are not, however, clearly marked but, instead, there are forms 

 at all times in all stages of development. The ripening of tlie fruit crops 

 makes this constant development possible. In June the mangoes are all 

 ripening and the maggots are living in these ; in the latter part of July and 

 August the mangoes gradually disappear and the guavas begin at the same 

 time to ripen, thus giving the flies an opportunity to continue their work ; 

 in October the guavas are replaced by the oranges. The late crop and the 

 early spring crop arc said to be continuous enough to maintain the fly. It 



iShowiiiy iiifeoted fallen 

 propagatiou of the fly. 



Figure 121. 



loft on the gri 



111(1, lluis favoring the uurestrietecl 



is stated by Mexican entomologists that the fly has no dormant period but 

 is continually developing and reproducing. This is put forth as a proof of the 

 impossibility of introducing the -pest into California, since they make the 

 point that there is a long period between our orange crops. As a matter of 

 fact, in one place or another ripe oranges may be found on our trees the 

 year through. 



The proportion of the fruit infected varies, of coutse, with the abundance 

 or the scarcity of the flies in any place and at a given time. In Chiapas the 

 infection is not great, although it is by no means negligable. In Oaxaca the 

 late oranges and mangoes are afifected quite badly while the early fruit is 

 scarcely touched. In Cordova the same condition exists. This would seem 

 to suggest that there is somewhat of a dormant period and a period when 

 the mass of flies emerge. In the state of Morelos the pest is most abundant 



