INSECT PESTS IN MAURITIUS. 189 



Mandarines suffer every year from attacks of the fruit-fly, Ceratilis catoiri, Gu6r. 

 The only remedial measure against this pest would appear to lie in the introduction 

 of parasites. 



Mango. 



Batocera ruhus, L. The larva of this Longicorn beetle causes appreciable damage 

 to various trees, amongst which is the mango. In certain cases trees heive been 

 found to suffer so severely that control measures had to be adopted. 



Eight to ten years ago a Cecidomyiid fly, Procontarinia mattciana, Kieff., found 

 its way into the Colony. It is known to occur also in India, and was probably intro- 

 duced accidentafly from that country. The insect is extremely destructive, and 

 wherever it is found the yield is reduced enormously, the leaves being infested when 

 they are stiH quite tender and about 2 inches long (fig. 1). At this stage smafl spots 



Fig. 1. Lower surface of mango leaf sliowiiig galls made by Procontarinia matteiana, Kieff., 



denote the places where the insect has oviposited. As the larva grows up in the 

 leaf tissue, a gall is formed ; the one harbouring the adult insect prior to its emergence 

 measures from 1 -5 to 2-0 mm. in diameter. The gall shows equally on either surface 

 of the leaf, but the fly emerges by puncturing the lower surface. Infestation is 

 usually very severe, as many as 150 to 300 galls being formed on a single leaf. They 

 occur in such large numbers that they touch one another, there being scarcely room 

 for more. The leaves affected in this way soon dry and fall off. The life-cycle of 

 the insect is about two months, its period of most common occurrence being from 

 November to June inclusive. 



Coccus mangiferae, Green, is quite common and sometimes occurs in great 

 numbers. After the Cecidomyiid, it certainly is the worst pest of the mango leaf. 

 The other undermentioned Coccidae cannot as a rule be regarded as regular pests. 

 These are : — Coccus hesperidum, L., Eiicalymnatus tessellatus, Sign., Chionaspis 

 dilatata, Green, Pseudaonidia trilobitiformis , Green, Vinsonia stellifera, Westw., and 

 Icerya seychellarmn, Westw. The last-named is sometimes quite common and does 

 a certain amount of injury. x\s a result of the combined attacks of scale-insects, 

 the leaves become covered with their honey secretions. On this covering there is 

 a dense growth of sooty mould [Capnodium sp.), which obstructs the stomata. The 

 leaves have a miserable appearance and cannot carry on their physiological functions 

 as they should, so that the whole tree suffers. 



