No. 4.] GREENHOUSE PESTS. 387 



kills the animals when they attempt to cross such bands toward the 

 plants. If for any reason it is not wise to use the lime, similar bands 

 of dry bran may be used, the animal in trying to cross such material 

 soon exhausting its supply of slime and becoming covered by the bran, 

 being rendered helpless and unable to move. Bran used in this way, 

 however, is successful only as long as it is dry, and when it becomes 

 wet must be replaced by a new supply. 



Red Spiders. 



These common pests are also not insects, but are mites, having 

 eight legs when adult, instead of six. They vary in color from yel- 

 lowish to dark brown, and sometimes have a greenish tinge. 



The red spiders spin a very delicate web, beneath which they live, 

 the web being difficult to see. They are most plentiful near the 

 midribs on the under side of the leaves, where they may frequently 

 occur in large numbers, sucking the plant juices. They move about 

 freely, however, and may travel some little distance in a short time. 



Their list of food plants is a long one, including tomatoes, cucum- 

 bers, carnations, roses, violets, and in fact most ornamental plants, 

 which they injure to varying degrees according to their abundance. 

 The eggs are deposited on the under side of the leaves, about five on 

 an average being laid per day, till each female has laid about a hun- 

 dred. These eggs hatch in three or four days in the warmest weather, 

 but in cold weather this may be delayed to about two weeks. It is 

 probable that from the time an egg is laid till the mite becomes adult 

 requires between three and four weeks. 



The Hemispherical Scale. (Saisselia hemisphcerica Targ.) 

 This is usually the most common soft scale found in greenhouses. 

 It is a brown "lump" in form, rather less than a fifth of an inch long, 

 and nearly as broad, and is found on many kinds of plants though 

 most abundant on palms, ferns and cycads. It locates both on the 

 leaves and stems, and in Massachusetts seems to be particularly 

 abundant on the Boston fern. Its life history does not seem to have 

 been completely worked out, but it probably breeds at all seasons 

 of the year, laying eggs which hatch into rather flat, pale-colored 

 young. 



The Soft Scale. (Coccus hesperidum Linn.) 

 This scale is similar to the last, but the young are apparently born 

 alive. It feeds on citrus plants, oleanders and many other green- 

 house plants. 



The White Scale. (Aspidiotus hederce Vail.) 

 The white scale has also quite a list of food plants, but is perhaps 

 as abundant on the ivy, palms and croton as any in Massachusetts 

 greenhouses. It is quite flat, having only a slight elevation at or near 



