Red Spider. 



335 



turned yellow in many grounds, and the yellowness Avas fast 

 spreading up the poles. 



Upon the under-surfaces of the leaves thick webs were 

 spread from mid-rib to mid-rib, under which the 

 mites were seen actively sucking up the juices. All sorts 

 ■and conditions were there, varying in size and differing in 

 •colour, but the greater number of them resembled the adult 

 specimen in the figure. Now and then one was seen of a 

 darker yellowish hue, approaching brown, but this was 

 exceptional. Many eggs, which are perfectly globular, were 

 suspended as it were in space between the mid-ribs, but 

 upon close inspection with a microscope it was seen that 

 they were kept in this position by means of fine threads 

 stretched from side to side. 



It was curious to note the instantaneous effects of rain, 

 two dull days, and a fall of temperature, upon the mites. 

 There was, naturally, an increased supply of sap to the 

 plants from the rain, which in a degree arrested the yellowing 

 of the leaves, but there was also an immediate and very 

 marked check to the harmful activity of the spinning mite. 



Life History. 



The spinning mite of the hop plant passes the winter in 

 the perfect state under stones and clods, in the bark of trees, 

 and in the clefts and under the dried rind of hop poles. It 

 is not noticed, at all events in numbers or as actively 

 injurious, unless there is at least normal summer-heat, and. 

 it only multiplies in a dangerous degree when the day and 

 night temperatures are abnormally high. In such circum- 

 stances the increase in its numbers and the rapid spread of 

 its harmful influence are remarkable. Eggs are abun- 

 dantly laid and, as above described, fixed in position by 

 threads. The comparatively large and round egg is pellucid 

 white at first and finally becomes slightly dark- coloured. 

 The mites emerge from the eggs in five or six days, and at 

 once begin to feed on the leaves. At first they are pale 

 greenish-yellow in colour, with dark patches on both sides 

 of the body ; they become more tinged with yellow later, 

 and some specimens have been found of a very light brown 



