LX BIOLOGICAL SOCIETY OF WASHINGTON. 



The mite {Phytoptus oldvorus) is elongate, honey-yellow, o. 14 mm. 

 long, and with two pairs of four-jointed legs, each terminating in 

 a curved spine, with opposing bristles. The eggs are laid singly or 

 in small clusters on the leaves. They are spherical, transparent, 

 with a yellow tinge, and hatch in summer in four days. The cast 

 mite skins adhere, as stated above, to the surface of leaf or fruit. 

 The food of the mite is the essential oil which abounds in the suc- 

 culent parts of citrus plants. It is stationary when feeding, but 

 moves actively, and wanders from one part of the plant to another, 

 especially to new growths. Thousands occur on a single leaf, 

 75,000 having been computed by Mr. Hubbard in winter time on 

 a leaf averaging fifteen square inches. They are still more nume- 

 rous in summer. 



Rust rings encircle the fruit nnich as the ecliptic does the earth. 

 There is a penumbral band between brightest sun and deepest 

 shade, indicating the preference of the mite for such half shade. 

 Frosts kill the mites, but not the eggs. Drouth causes" both to dry 

 up. Birds, insects, and especially spiders, are the chief agencies 

 in distributing the mites from place to place. The effect of the 

 mite on the fruit, aside from the rusty appearance, which lowers 

 the market value, is in nowise injurious, as the quality is, if any- 

 thing, improved, and the disposition to rot decreased. The effect 

 on the leaf is to slightly check growth. 



The mite is generally distributed in Florida, but not elsewhere. 

 Like most mites affecting growing plants, it is worse on high, dry 

 lands than in low, moist ones. 



No method of culture or of manuring — in fact, no method that 

 does not comprehend the true cause, has proved of avail to pre- 

 vent the rust. Wind-breaks and isolation act as preventives, but 

 insecticides aro the only remedial agencies ; they must, however, 

 kill mites, eggs, and molting vi\\\.Q.%. Whale oil soap, one pound to five 

 gallons of water, in early spring before new growth begins, and weaker 

 solutions at frequent intervals, cause the mites to fall to the ground. 

 Flozvers of siilpliitr is deadly to the active mites, but not to the itgg'r.. 

 Kerosene emulsions, as used against scale-insects, with sulphur 

 added, are the most satisfactory. 



Dr. E. P. Rowland read a paper on The Effect of Anaes- 

 thetics ON Animals, explaining the new invention of Paul Bert. 



