INSECTS AND DISEASES AFFECTING PLANTS. 277 



ing, and are generally found in dark or ill-ventilated 

 greenhouses, adhering to the stems and under part of the 

 leaves of hard-wooded plants. The best remedy is fir-tree 

 oil, used as described for Mealy Bug. 



Thrips is an active insect, varying in size from that 

 hardly perceptible by the naked eye, to the size of the 

 Green Fly, and varying in color from whitish-yellow to 

 dark brown; it is a jumping insect, very active in its 

 movements, and when it once gets a foothold is very de- 

 structive. It succumbs to tobacco smoke, but not so 

 quickly as does the Green Fly. It luxuriates in shaded 

 situations, and is generally found where plants are stand- 

 ing too thickly together, or where the ventilation or light 

 of the greenhouse has been deficient. I think it may be 

 safe to assert that in any well-regulated greenhouse or 

 hot-house no injury from insects will ever become serious, 

 if proper attention to syringing and fumigating has been 

 given. Syringing, or other means of keeping a moist at- 

 mosphere, must never be neglected for a day, and fumi- 

 gating by tobacco smoke should be done, at the least, 

 once each week. The application of fir-tree oil will also 

 quickly check Thrips or Aphis. 



The " Carnation Twitter." This is an insect fortu- 

 nately but little known, and called in this district only 

 by its local name of " Carnation Twitter, "given from its 

 rapid and nervous motion. As seen by the naked eye it 

 is about the twentieth part of an inch in length, and of a 

 thickness not more than that of a cambric needle. It is 

 of various shades of color, from green to black; it is never 

 very numerous on the plants, but most destructive and 

 evidently poisonous in its attacks on all varieties of the 

 Carnation and Pinks. 



Its effects on the Carnation somewhat resemble those 

 of the Eed Spider, except that when attacked by the 

 "Twitter," the leaves have a cankered and twisted ap- 



