LIFE-HISTORY AND METAMORPHOSES. 3 



a fact most noticeable in Mytilaspis pomorum and 

 Lecanium persicae, Fabr. If we take the former we 

 find, although it occurs most freely upon standard 

 trees, it rarely infests them to such an extent as to cause 

 serious injury, its attacks being chiefly confined to the 

 trunk and main branches ; whereas, if it once estab- 

 lish itself upon a tree trained against a south wall, the 

 insects in time will cover every branch and twig, and 

 finally will attack the fruit and leaves also. The 

 effect of still more favourable conditions is even better 

 illustrated by Lecanium persicde. This insect is 

 usually found wherever the peach and nectarine are 

 cultivated, but outdoors I have never found it in 

 sufficient numbers to cause injury to the trees ; under 

 glass, however, it increases at such an enormous rate 

 that it becomes a matter of great importance to keep 

 the insect in check. 



In spite of the apparent increase of individuals 

 under favourable conditions, the vitality of certain 

 tender exotic species, when exposed to frost, is most 

 remarkable. I have known various stages of Diaspis 

 lromeJid3,KeT., to endure frost for several days, and have 

 subsequently reared a number of the males by placing 

 them in a temperature of about 70 F. I have also 

 known " mealy bugs " to survive the winter outdoors 

 on the ivy-clad wall of a hothouse, which no doubt 

 afforded them material warmth and shelter, but could 

 not have shielded them from the severe frosts to 

 which they were exposed. Under such conditions 

 they did not increase in numbers, and I have little 

 doubt that in time they all succumbed to the exposure. 



Like plants and trees, our indigenous Coccids rest 

 throughout the winter, some in the egg, others in the 

 larval, and a few in the more advanced stages ; but 

 none, to the best of my knowledge, pass the winter in 

 the adult stage, and, so far as I am aware, all the 

 species are single-brooded. The species infesting 

 plants under glass in warm houses have no resting 

 season, successive broods occur throughout the year. 



