86 TEINIDAD AND TOBAGO BULLETIN. \XVIIL 2, 



but it may occupy several weeks. Belated species of thrips have 

 been known to live from 34 to 84 days in captivity. Generation 

 is continuous and every 20 daj's there can be a new brood. At 

 this rate the increase of thrips is very large and quick and the 

 progeny of a single female might reach a million in a couple of 

 months. See figm-es 1-4. 



FOOD PLANTS. 



The cacao thrips is also found on the following plants : hog plum, 

 mango, guava, avocado, ahiiond {Tcrminalia catajypa), mammy apple, 

 cashew, roses, pois doux and pomme rose. All these plants are 

 restricted to certain seasons for the putting out of new leaves and thus 

 form continuous favourable breeding grounds for thrips during the whole 

 year. There are many other thrips to be found on the cacao and other 

 plants mentioned, but most of these do no harm. The cacao thrips does 

 not occur in flowers ; the black thrips so often found in the flowers of 

 the Bois Immortel and even cacao are different species and are not 

 injurious. 



SEASONAL HISTORY OF THRIPS. 



As with many other insects the increase of thrips depends on the 

 abundance of its food plants and on the condition of the leaves that are 

 best suited to it. From continued observations since 1909 I And that 

 thrips in all stages prefer the young leaves of their food plants although 

 they can exist on fully mature leaves. Different kinds of trees put out 

 young leaves at different times but a great many, and among these 

 the cacao trees, put out their new shoots and leaves during the rainy 

 season. It is then that the thrips commence their multiplication on 

 cacao. Previous to that and during the dry season thrips will exist on 

 such food plants as put out new leaves then, for example mangos and 

 almonds ; or they will attack stray cacao pods or such stray cacao 

 suckers as exist. As far as cacao is concerned we can say that the 

 thrips season begins with the rainy season and that the maximum 

 multiplication takes place just after the heavy rains of May, June and 

 July ; roughly speaking it may be stated that thrips begin with the 

 setting of the cacao crop. All the time the leaves are young and not 

 too tough and the rains are still on, thrips remain at the tops of the 

 trees, but when the weather becomes drier they descend to the shaded 

 pods and suckers and can be found on these right through the dry 

 season. A certain degree of moisture appears to be necessary for the 

 well being of tln-ips. At the height of the dry season they are at their 

 lowest ebb but still never disappear entirely, and if cacao does not 

 offer suitable food they will migrate to other host plants that happen 

 to be in tender foliage at that time. In this connection mangos, 

 almonds, hog plums, and cashew should be watched. During sjiells 

 of dry weather damage from thrips becomes more apparent, but 

 extensive multiplication and feeding take place during damp weather. 

 In the following table an attempt is made to show the seasonal 

 history of thrips and the food plants on which they are likely to be 

 found. The rainy and dry seasons can only be taken as approximate. 



