GREENHOUSE PESTS 125 



plant. The knobs shown contain the young eelworms 

 7V inch in length, which increase in size until they become 

 pear-shaped. They then lay eggs on other parts of the 

 root or on a fresh plant and re-assume their worm-hke 

 form. Soil infested badly must be saturated twice in 

 carbohc acid solution on two successive fortnights, and 

 left to sweeten out for at least six weeks. Gas Ume is 

 employed as a second remedy. It should be noted 

 that clover, grasses and many weeds and other plants 

 act as intermediary hosts for the preservation of eel- 

 worm, which fact will account for its appearance where 

 it could not have been otherwise explained. (See Plate 

 27.) 



In all these fungoid diseases half the battle in avoiding 

 them consists in the scrupulous cleanHness spoken of at 

 the beginning of this chapter, and before re-stocking a 

 house a fumigation of sulphur is a good thing as an 

 absolute fungicide. 



We may conclude our chapter with the White or Snowy 

 Fly, a hemipterous insect known to science as Aleyrodes 

 proletella, which is of common occurrence both inside 

 the greenhouse on tomatoes, cucumbers, etc., and on cab- 

 bage and other crops out of doors. See remarks in Chap- 

 ter III on cabbage pests. In houses the blight may be 

 removed with tobacco fumes. (See Plate 14b.) 



Some people think that Ants (Formicidae) are a great 

 nuisance, though I cannot see why, except in the case of 

 the Httle House Ant (F. domestica) which gets into cup- 

 boards where jam and honey are left uncovered. 



The main business of the yellow and the black ants 

 which we find in greenhouses crawhng up the stems of 

 the plants is to hunt for small beetles to eat and aphides 

 to " milk " of their honey dew. Loosened paths and 

 spaces behind shrunken skirtings in old structures afford 

 them house room. Naphthalene and seaUng up such 

 spaces with putty will do what is wanted. (See Plate 

 3, Fig. 5, and Plate 26.) 



