GREENHOUSE PESTS 121 



male, wingless as well. It seems rather late in the day 

 for paterfamiHas to turn up, in the third generation, but 

 apparently they can carry on within certain hmits with- 

 out him altogether if need be, as they go in for what we 

 call parthenogenesis or virgin reproduction. The result, 

 however, of the appearance of the male on the scene 

 creates a diversion, as we might expect, and at this stage 

 the winter egg is produced, which the parent louse deposits 

 on the bark and colours so artfully that it cannot be seen. 

 These eggs carry the species through the cold months. In 

 April they hatch into a " stock-mother " who creeps up 

 the branches and into the buds, where her sharp proboscis 

 sets up a gall-hke sweUing within which she estabUshes 

 herself and brings into being some 200 children, all females, 

 but some are bud-dwellers and the remainder take after 

 the original root -infesting great-grandmother once again. 

 Thus the " grand circle " is complete, in the sixth genera- 

 tion from the commencement. I hardly think there is a 

 more wonderful story in the whole of the animal king- 

 dom, nor a more tenacious method of ensuring the con- 

 tinuance of a species. Hence the difficulty of eradicating 

 phylloxera. In bad cases Vines must be uprooted and 

 burnt, the soil removed and the house fumigated by the 

 cyanide process. 



The power of these parthenogenetic females to repro- 

 duce, does, after a time, diminish, and thus the arrival of 

 the male certainly adds vigour to the race. It is evident 

 that the sex problem among the phylloxera is in a very 

 rudimentary state. 



As regards remedies it will at once be evident that the 

 winter egg is the weak spot at which to break the chain, if 

 you can find it, but there's the rub. It is coloured to 

 match the bark, but good results will be obtained by the 

 use of one of those rust-removing brushes made of steel 

 wires and sold by toolmakers. After this caustic potash 

 may be applied. 



I might mention that a single stock-mother, com- 



