INSECTS OP THE GREENHOUSE. 313 



the ventilators are kept closed for awhile on bright 

 mornings and the walks and plants thoroughly syringed, 

 the conditions will be unfavorable to the red spider and 

 the numbers can in this way be reduced. When the 

 warm days of spring and summer come on, a similar 

 treatment in the afternoon is often advisable. Another 

 remedy that is entirely effectual and quite easy to use 

 is evaporated sulphur. If this is applied thoroughly 

 once or twice, it will rid the plants from these pests. 



THE THRIPS. 



The insects grouped under this name, although 

 quite small in size, are often the source of considerable 

 trouble in the greenhouse, as well as upon 

 fruits and grains. They have long, slender 

 bodies (Fig. 109) and generally four wings; 

 these are also long and narrow and of nearly 

 equal size and shape, with a fine hair-like 

 fringe around their edges. In most cases the 

 wings are without veins, except, perhaps, one 

 or two longitudinal midribs. The antennae 

 are long and slender, with generally from 

 seven to nine joints. In their mouth parts 

 ,hey resemble both the true bugs and the Orthoptera, or 

 grasshopper group, as they are "adapted for both biting 

 and sucking. They resemble the adult in both the lar- 

 val and pupal forms, and when full grown they are 

 slightly less than one-tenth of an inch in length. They 

 are sometimes light yellow, but are generally brown or 

 black, with the extremity of the abdomen in some cases 

 bright red. The antennas and legs are usually light 

 colored ; as larvae and pupae most of the forms are of a 

 yellowish-white. 



Thrips do considerable injury in the greenhouse, as 

 they eat holes in the leaves and flowers and suck the 

 juices. They are especially injurious to the rose, car- 



