REPORT OF THE ENTOMOLOGIST. 



339 



together with good results. It is thought that by mixing in this way loss floor will 

 suffice. Three-eighths of a pound of London purple to one barrel of water may be 

 taken as a suitable percentage. Three-eighths of an ounce may be used as an equiv- 

 alent in one bucketful of water. The amount of this poison was reduced to One-fourth 

 of a pound to the barrel with good effect, but this seems to be the mini mum quantity, 

 and to he of value il must be applied in favorable weather ami with unusual thorough- 

 ness. With one-half or three- fourths of a pound to the barrel, about the maximum 

 strength allowable is attained, and this should be applied only as an extremely line 

 mist, without drenching the foliage. 



Effects of the mixture. — The Hour seems to keep the poison from taking effect on the 

 leaf, preventing to some extent the corrosive injury which otherwise obtains when 

 the poison is coarsely sprinkled or too strong, it also renders the poison more per- 

 manent. On the leaves, especially on the uuder surfaces, the London purple and dour 

 can be seen for several weeks after it has been applied, and the insect is not only de- 

 stroyed, but is prevented from reappearing, at least for a long period. By poisoning 

 again, a few weeks later, the insect is deterred with greater certainty for the entire 

 season. By being careful to administer the poison before the insect has worked, and, 

 above all, to diffuse the spray finely but not in large drops, no harm worth mention- 

 ing will accrue to the plant from the proportion of poison recommended. The new 

 growth, that developed after the first poisoning, was protected by one-fourth of a 

 pound to the barrel in 18H2. Fr m midsummer until autumn the unpoisoned half of 

 the grove remained denuded of foliage, while the poisoned half retained its verdure. 

 The litti.' damage then appearing in the protected part was mostly done before the 

 first treatment. Eggs were laid abundantly throughout the season. Many of these 

 seemod unhealthy and failed to develop, probably because they were poisouod. Many 

 hatched, but the young larva? soon died. The eggs were seldom deposited on the 

 young leaves that were appearing after the poisou was applied, but were attached to 

 the developed leaves, and here the larvae generally got the poison to prevent their at- 

 tack upon the aftergrowth. Still the young leaves became perforated to some extent. 

 The adults, which By from tree to tree, appeared plentiful without much interrup- 

 tion throughout the season, and often several could be seen feeding on each tree. 

 Possibly many of these may have become poisoned before depositing the eggs. 



The efficiency of London purple being established, it will generally be preferred to 

 other arscnicals, because of its cheapness, better diffusibility, visibility on the foliage, 

 &c. As the effecls of the poisons commonly do not appear decidedly for two or three 

 days after their administration, the importance of the preventive method of poisoning 

 in advance cannot be too strongly urged. As the effect is slow in appearing, impatient 

 parties will be apt to repoisou on the second or third day, aud thus put on enough to 

 hurt the plant when the effect does come. Much depends on dryness or wetness of 

 the weather ; but good effects may be expected by the third or fourth day. 



Ill the same report is figured (Hate VI) a simple apparatus which 

 was used to good effect iu spraying the trees and which was explained 

 in detail- in the text (pp. ICS, 169). It is in brief a barrel pump contain- 

 ing a stirrer-bar, attached by a loop to the swinging end of the pump, 

 and which by its oscillations constantly stirs the mixture. The barrel 

 rests upon a skid in the bottom of a light cart in which it is drawn from 

 tree to tree. To the nose of the pump is attached a long, slender rubber 

 hose. To enable the operator to thrust the hose up among the branches 

 of the tree, it is run through a long bamboo pole the septa of which 

 have been burned out by a hot iron rod. At the end of the hose is a 

 short metallic rod to which one of the cyclone or eddy-chambered noz- 

 zles has been attached. , 



By the use of such an apparatus, which is comparatively inexpensive, 

 a great many trees can be thoroughly sprayed in the course of a day. 

 Such a course requires labor and some expense, but the result can be 

 accomplished in no easier way. 



DESCRIPTIVE. 



We have already given the general appearance of the egg, and the 

 larva will be readily recognized from the figures (Plate VIII, Figs. 1, c?, 

 /). It is practically indistinguishable from the larva of the closely 

 allied Plagiodera lapponica which feeds upon Willow at the North, but 

 the larva of the latter species emits the milky fluid more freely aud has 



