20 INSECTS INJUKIOUS TO SUBTROPICAL FRUITS. 



infested, and in such cases the larvae move around to the other side 

 and feed. Thus the function of the leaf is entirely destroyed and 

 the leaves dry up and often fall. (See PI. IV.) In feeding, this thrips 

 excretes over the surface of the infested leaves a reddish fluid in small 

 spots, which hardens and turns black. Although it has not been 

 observed on the fruit, it is probable that in cases of severe attack this 

 insect will also attack the fruit of the mango and avocado in the same 

 manner that it does the pods of cacao. If such a condition should 

 result, it will produce even greater loss, since the value of these high- 

 grade fruits will be greatly reduced. The effect of the feeding is 

 graphically shown in Plate IV, where the leaf on the left is uninjured 

 and the leaf on the right has been infested by thrips. 



ORIGIN AND DISTRIBUTION. 



Heliothrips ruhrocindus was originally described from specimens 

 collected in the island of Guadeloupe, French West Indies. At about 

 the same time it was observed to be injuring cacao on islands of the 

 British West Indies — Grenada, St. Vincent, St. Lucia, and Dominica. 

 Maxwell-Lefi'oy, in Indian Insect Life, wi-ote: "Physoj^hus ruhrocincta 

 Giard is a serious pest to cacao in the West Indies, to which place 

 it was probably introduced from Ceylon." There has been some 

 question as to whether the thrips which injures cacao in Ceylon is 

 this same species, but as the author quoted above was one of the 

 first to study this species in Grenada it is hardly probable that he 

 would mistake another insect for it, provided he saw the insect in 

 Ceylon that he refers to this species. 



This thrips occurs also in Trinidad, the island of Tobago, the Virgin 

 Islands, and the Uganda, and within the past year has been recorded 

 from the Hawaii Experiment Station greenhouses in Honolulu. 



In the United States it is confined to a short strip of the Florida 

 east coast centering in Miami. As it is a tropical species, it will 

 probably not spread north of Florida; therefore, unless it obtains an 

 entrance into California or into greenhouses in the North the distribu- 

 tion in our own country will be limited. This insect has been taken 

 in one of the greenhouses of the Department of Agriculture on plants 

 from Mauritius. At present it is quite widely distributed in the 

 tropical islands of the Atlantic and Pacific Oceans, and its original 

 home was, without a doubt, in some of these islands. It may have 

 first come from Ceylon, as Maxwell-Lefroy suggests, or its original 

 home may be in the West Indies. Its habitat is the Tropical Life 

 Zone, as designated by Dr. C. Hart Merriam.« 



a Life Zones and Crop Zones of the United States. Bill. 10, Biol. Surv., U. S. Dept. Agi-., 1898. 



