STATE HORTICULTURAL SOCIETY. 203 



of these insects : occasionally wheat and corn are injured somewhat seri- 

 ously in certain localities. Green-house and other in-door plants, if not 

 carefully watched, are likely to be injured by them, but a little precaution 

 combined with a knowledge of the proper remedies and preventive mea- 

 sures in such cases generally suffice to eradicate them. 



If the latter part of the winter is open and the spring warm, bringing 

 them out in advance of their enemies, they are then more apt to be abun- 

 dant and injurious than ordinarily, as they are thus enabled to get the 

 start of the latter, and the ascendency thus obtained is not easily over- 

 come. The true Aphides are generally quite sensible to cold, being 

 largely destroyed by heavy frosts and severe cold spells ; but, as has already 

 been shown, there are exceptions to the rule ; and it is more than likely 

 that this result depends, in part at least, upon the effect the cold has upon 

 the plant on which they reside. Some, and possibly most of the woolly 

 species, appear to be less easily injured by the cold than the former ; but 

 it is quite natural this should be so, as the former reside chiefly on the 

 foliage, while the latter are found chiefly on the stems, branches, trunks 

 and roots. 



It is supposed by many that the insects of this family are easily 

 affected by water, but Curtis states that he "has been surprised to see 

 how slightly they are affected by wet ; " that " some Aphides attached to 

 a willow twig were immersed in water for sixteen hours, which did not 

 appear to incommodate them in the least, for, on being taken out and 

 placed in the sun, they increased and multiplied shortly afterwards." 

 Yet other species immersed but for twelve hours were destroyed, showing 

 a wide difference in species, in this respect. The experiments tried in 

 France upon the Grape Phylloxera indicate the inefficiency of this agency 

 in destroying this pest, as will be seen from an extract hereafter given. 



The author quoted above also further remarks that " their capability 

 of resisting some gases or effluvia is very astonishing ; for instance, I 

 corked some up in a quill containing a piece of camphor, which produced 

 an atmosphere that killed most insects in an hour, but the Aphides were 

 walking about unaffected after being confined there for twenty-four hours." 

 The fumes of tobacco and sulphur are, perhaps, the most potent gaseous 

 agencies in destroying them which are susceptible of general practical 

 application. Alkaline substances in powder or solution, acrid solutions, 

 kerosene and oils, are generally fatal to them, if they can be applied 

 directly. 



Dr. Harris states that "lice multiply much faster, and are more 

 injurious to plants, in a dry than in a wet atmosphere." That, as a 

 general rule, plants are more easily injured in dry than in moist weather 

 is undoubtedly true; but, as to the other part of the statement, I think he 

 is certainly mistaken, as a rule, for there is scarcely an individual, who 

 has paid any attention to this matter, that is not aware that a warm humid 

 atmosphere is favorable to their increase; yet there are some species which 

 appear to be more abundant in dry seasons. Curtis, the great English 

 entomologist, from whose writings I have already quoted, remarks, in 

 speaking generally of the Aphides: " Their increase in damp and sultry 



