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l68 PHASEOLUS VULGARIS (pRENCfl BEAn) 



In Mauritius and Reunion the bean, together with the 

 cow pea, amberique, &c., are attacked by a small fly 

 {Agroniy:::a phaseoli), which is tlie cause of this crop only 

 being grown at certain periods of the year. 



This insect lias been known in Reunion for a very long 

 while, as is shown by a note of Joseph Hubert's, dated 

 March 12th, 1800, and published by M. Boname in his 

 annual report for 1906-07 : — ■ 



" I fear the insects, and I am going to begin observing 

 them, for a number of observations have already proved 

 to me that what is attributed here to phenomena of growth, 

 to the varying success of different plants in winter or in 

 summer, in localities dry or wet, in the highlands or lowlands^ 

 is in reality the work of insects. In December, the month, as 

 regards temperature, furthest removed from July, when beans 

 are usually planted, I have seen magnificent beans which, 

 more often than not, perish after flowering. Very well, if 

 such is the case, observe the stalk of the plant ; you will 

 find it full of cracks, and looking closer you will further 

 see some grubs, small chrysalids whence emerge small black 

 flies. Taking the stem of a bean before the flies had flown 

 away, I saw eleven at once." 



The above note was transmitted to M. Boname by my 

 friend, M. A. de Villele. 



This little black fly lays its eggs upon the epidermis of 

 the plant as soon as the bean shows tw-o leaves; the larva 

 detaches the epidermis in which it lives and makes descend- 

 ing galleries. When the number of larvae harboured by 

 the plant is not a large one it protects itself bv means of 

 nodular galls, which enable it to withstand the insect's 

 attack; but the vield is diminished notwithstanding. 



The existence of this insect has been recorded in Australia 

 towards 1898, and it has had to be contended with in that 

 country. Its habits vary in the different countries of its 

 occurrence, and even in different districts in the same country. 

 In Mauritius, where it is found throughout, its occurrence iV 



