22 



broods in a year, and each brood may be said to extend over three or 

 four months. Therefore these insects are generally to be found in all 

 stages of development on the trees, which is due to the fact that the 

 separation into distinct broods is often more or less confused, as one 

 generation overlaps the next. 



M»ans of Dispersal, 

 Several agencies effect the spread of scale insects from tree to tree. 

 Among these may be mentioned the wind, insects, and birds. 



Preventive Measures. 



The best means to insure a tree from the attacks of scale insects, is 

 to endeavour by all possible methods to promote its vigour. Scale in- 

 sects attack w r eak trees first, and any lack of food or water will lay a 

 plant open to their attacks. 



As a preventive against scale insects, judicious pruning is also very 

 necessary, for they thrive best where ihey are protected from the 

 direct sunlight and a free circulation of air. It is therefore necessary 

 that the trees be kept from a dense matted growth of clustered 

 branches and twigs, for such parts are more likely to be affected by 

 scale ; for the same reason trees sh> uld not be planted too close together. 



In Jamaica our heavy seasonal rains act as a considerable check to 

 scale insects, at which period they will be found to be less active. 



Natural Remedies. 



In the United States, natural remedies are encouraged, and artifi- 

 cial means used to keep a check on the attacks of scale insects. The 

 natural remedies are the encouragement of other insects that prey on 

 them. Foremost among these are the larvae of the ladybird beetles. 

 Where not already existing, these beetles are sometimes introduced 

 into districts to prey on the scale insects, and in some cases with the 

 greatest success. So much so that sometimes artificial remedies are 

 found to be unnecessary. 



Another important class of natural enemies found to be very des- 

 tructive to these pests, and to keep them well in check, are some 

 hymenopterous parasites These are four winged parasitic flies, the 

 larvae of which feed within the bodies of the scale insects. Less im- 

 portant among the insect enemies to scale insect may be mentioned 

 the Lace-v\inged flies, a few r parasitic dipterous flies, and the larvae of 

 several species of Lepidoptera. 



Very little is known of what natural enemies to scale iD sects there 

 are in Jamaica, but that some are present is certain, for *-ome larvae 

 of a ladybird beetle were seen crawling over scale insects that were 

 lately brought to the Museum, which were infesting orange trees. 

 And a foimer Curator has observed the same species of scale, Myti- 

 laspis citrtcola to be parasitised by some Hymenopterous insect. But 

 from the abundance of scale insects in Jamaica, it appears likely that 

 they do not suffer much from natural enemies. In the future it might 

 therefore be found advisable to import from the United States or else- 

 where, some of their natural insect enemies. Such that would prove 

 useful for this purpose would be some of the ladybird beetles, and the 

 parasitic Chalcididae and Mymaridae flies, and as the habits of these 

 predaceous and parasitic insects are well known, there would be no 

 reasonable objection to their introduction here. 



