GREENHOUSE PESTS 109 



of temperature, which must be kept absolutely constant 

 if any measure of success is to be obtained. These struc- 

 tures are sometimes allowed to become very hot at midday 

 and to suffer a corresponding big drop at midnight, in 

 which case it is no wonder if plants sicken or die. A 

 thermometer should be placed at each end, the place well 

 ventilated when the sun is up and the fire seen to before 

 retiring for the night. Class your plants according to the 

 temperature they require and grow them as near to the 

 light as possible. 



But supposing all this has been carefully attended to, 

 there is still another cause of failure, viz. the ravages of 

 insects, whose ingenuity in getting into a greenhouse or 

 ground frame is sometimes extraordinary. You may 

 think there is no nook or cranny through which the tiniest 

 parasite can possibly creep. He will be there all the 

 same. One very patent thing about insects is their 

 abiUty to enter or escape through incredibly small holes 

 in comparison to their size. In my early days, Uke many 

 boys, I used to go butterfly hunting, and frequently got 

 the net torn in the brambles, so that after a few accidents 

 of this sort a needle and thread was always part of my 

 equipment on these expeditions. It had been most 

 exasperating when, having captured a fine Painted Lady, 

 I found her whistling away through the net and across 

 the clover with a merry laugh, as much as to say, " Thought 

 you'd got me, I suppose ? " Yet the hole through which 

 her ladyship managed to squeeze would scarcely have 

 allowed a halfpenny to pass. 



That is how they get out. With a greenhouse it is a 

 case of getting in. It is surprising how the news spreads 

 through the insect world as soon as your latest model of 

 the Crystal Palace is erected and the workmen have left. 

 One would think there were flying journalists and editors 

 with bristUng antennae to wireless full particulars a 

 fortnight in advance. And of course if you go and pro- 

 vide a tropical temperature in an arctic climate you must 



