280 



Insect Pests. 



LIFE-HISTORY AND HABITS. 



This acarus belongs to the genus Brydbia, which is easily told 

 from the Bed Spider of plums, hops, etc., Tetranychus, by the first 

 pair of legs being much longer than the rest, and all the legs longer 

 than in Tetranychus. 



In colour this mite is very variable : some are grey, others greenish, 

 others rusty red ; some have red and brown coloration, yet others 

 leaden grey or bright red ; the legs are pale or dull reddish. In size, 

 large mature specimens may reach nearly ^ inch. 



They collect in dull weather in early spring in crevices on the 

 wood or under the loosened skin upon it. So densely are they often 

 packed together that they look like one red 

 mass, their legs tucked under their bodies. 



I have noticed that in this stage they are 

 frequently of a rich red hue, almost crimson- 

 lake. I have found them like this early in 

 February, both in Kent and Cambridgeshire, 

 in a semi-dormant condition. As soon as the 

 young leaves show they are ready to move, 

 the first warm sunny day they get on to the 

 leaves and commence to feed and gradually 

 mature. At night they return to their shelter, 

 and also on dull damp days. They feed 

 mainly on the undersides of the leaves, and 

 the attack usually seems to start in the 

 centre of the bushes and spreads outwards. 



In April or even March they may have started to reproduce, when 

 minute round globular shiny reddish eggs are laid on the twigs, base 

 of the thorns, and on and between the old bud scales. These eggs, 

 which can only be seen with a magnifying glass unless laid in 

 large masses, hatch in four or five days into small semi-transparent 

 young with six legs, these soon commence to feed, in another four 

 days moult and become like the adult; two more moults appear to 

 take place, and then at the end of twelve to fourteen days they are 

 ready to reproduce again. 



What happens between June and the following February is not 

 definitely known, but one may find the ova and immature mites on 

 the wood at Christmas, and it is probable that most of the eggs laid 

 in June remain until the winter, and that a few only hatch out before 

 Februarv and March and hibernate on the bushes. What regulates 



[F. K. 

 FIO. 191.-THK IVY I5KI> 



(Greatly enlarged.) 



