FAMILY APHIDID^. 161 



A species of Thrips infests the If ernel of wheat while in its milk state ; and it is quite 

 doubtful whether this one can be destroyed by the application of fine slaked lime, as has 

 been recommended : still, w^hen the dew is on the plant, a free sjn'inkling may be tried, 

 which, if not successful in the way designed, will at least benefit the soil. 



The disease called appletree blight is due to another genus of aphides, the Eriosoma. 

 It is a woolly insect, destitute of wings, but is wafted from tree to tree by the buoyancy of 

 its woolly envelope. The eggs, only visible under a microscope, are enveloped in a cotton- 

 like substance found in crotches of the tree and chinks of the bark ; and if there are 

 suckers standing around the tree, it may be found on them also. The full-grown insect is 

 one-tenth of an inch long, emits a sticky juice from its extremity, and is covered with 

 flakes of down : when this is removed, the color of the antennae, head, sucker, and spines 

 is blackish ; abdomen honey-yellow ( Harris). It feeds upon the sap of the alburnum of 

 the apple-tree ; and the wounds it inflicts give origin to warts, excrescences, and inequali- 

 ties upon the bark : the final result of its attack is the death of the tree. 



It appears from the accounts which have been published of the ravages of this aphis in 

 England and in this country, that the only hope of arresting the evil lies in beginning at 

 once, or as soon as the insect makes its appearance. After it has extended itself far and 

 wide upon the large trees of an orchard, it becomes exceedingly diflicult to arrest its 

 progress, and this probably only happens in cases when the weather becomes unfavorable 

 to the life and propagation oi the insect. The rational way to go to work, will be to scrape 

 thoroughly all the trunks and larger limbs, and then to scrub the surface with strong 

 soapsuds, or whitewash them. When the trunk beneath the soil and the roots are infested, 

 extend the treatment to these parts also. Mr. Harris recommends a solution of potash, 

 and to protect all the wounded parts by grafting wax, and also the removal of all refuse 

 from and about the tree that may contain the eggs or the living animals : cut off, like- 

 wise, and burn all the smaller limbs. It seems that all strongly scented solutions, such as 

 tobacco water, ammonia, etc. are more or less effectual remedies against the depredations 

 of the various kinds of aphides. 



Another interesting and important fact in natural history is that plant-lice have nume- 

 rous foes, that prey upon and destroy them in great numbers : among these foes we may 

 rank the numerous species of Coccinella, or ladybirds (See Plate xi, where several of the 

 most common kinds are figured). A person unacquainted with these small and beautiful 

 insects, on seeing them upon an infected plant, might mistake their characters and office, 

 and attribute to their presence the sickly state of the plant. He could not well commit a 

 greater mistake ; and to convince himself of this, he would only need to watch the move- 

 ments of the little beetle for a short time, when he would find that its errand was one of 

 kindness to him and his plant, for he would soon observe it feeding upon the plant-lice : 

 these constitute its food, both in the larva and mature states, so that its services in re- 

 [ AeBicuLTURAi. Eepobt — Vol. v.] 21 



