CHARACTERS OF THE GENERA OF APHIS AND COCCUS 91 
water be forcibly applied ; by this they are dispersed and annoyed, and 
if frequently so disturbed are at last completely banished. It is also 
said that if a house infested by them be filled with steam, raised from 
highly heated flues, and closely shut up for an hour or two, they will 
be destroyed; or if the house be filled with the fumes of sulphur smeared 
on a hot flue, the result is equally fatal to the Acarus. 
By these means, timely and repeatedly administered, plants in 
houses may be kept free from this little plague, and so frames may be 
defended from them ; but if they take to peach or other trees on the 
open walls, the garden water-engine must be in frequent requisition 
to disperse them. 
The above history relates to that species of Acarus better known by 
the name of Red Spider. Several others are found in gardens and 
fields, but they are unnoticed except by entomologists, because they do 
no very visible mischief. Some of them live among decayed vegetable 
matter, and others on the leaves of grass. Those yellow patches seen 
in the herbage of a meadow in the month of October, are caused by 
colonies of these Acari, which deprive the grass of its colour. 
The deciduous bark of the vine forms a safe hiding-place for insects 
of this small size during winter ; and therefore there is not a more 
beneficial practice in the culture of that plant, than ^keeping it 
constantly free from the loose strips of dead bark. 
We know nothing of the economy or natural history of this genus of 
insects, further than js stated above. Whether oviparous, like the 
spider, or viviparous, like the Aphis during summer, is to us unknown. 
An entomologist who has leisure, and who can have access to a peach- 
house during the three first months of forcing, and furnished with 
a powerful glass and a good share of acuteness and patience, might 
probably (if it be not done already) see into their economy so far as 
to be able to assist the gardener either to keep them off, or to destroy 
them in the first stage of their life. 
An equally pernicious insect among stove-plants, is another one called 
the Thrip. It is of a pale greenisli-white colour, smaller and longer 
shaped, and more active than the Aphis. 
(To he continued.) 
Sir, —In your last number I perceive that you request information 
as to the characters of the genera of Aphis, Coccus, dye. Should no 
one else have responded to your call, the following descriptions are 
much at your service. 
The British destructives in question belong to the order Hemiplera 
