29 



These span-worms reach their full growth in May and then enter the 



earth to a depth of from two to four inches; here each one forms a smooth 

 cell, but does uot spin a cocoon. The chrysalis state is assumed a few 

 days after the cell is completed, but the moth does not issue until the 

 following winter or early spring. The chrysalis is of the usual form, 

 of a dark reddish brown color, and the posterior extremity bears two 

 diverging spines; the tips of the wing-cases almost reach the posterior 

 end of the fifth abdominal segment; length, 14 mm . 



Perhaps the most important enemies of these span-worms are cer- 

 tain kinds of insectivorous birds, particularly the black birds, which 

 1 repeatedly observed in. the infested trees, and Mr. Cooper informs 

 me that he has seen one of these birds carrying four of the span- 

 worms in its beak. Of internal parasites, only one species is at pres- 

 ent known to me to attack these span-worms; this is a small black, 

 four- winged fly belonging to the genus Apanteles. The sides of its 

 abdomen are largely yellow, the front and middle legs, including their 

 coxse, are also yellow, while the hind legs, with the exception of the 

 tips of the femora and tibiae, and the whole of the tarsi, are of the 

 same color. I found several of the white cocoons of this parasite 

 attached to the trunks of the infested trees on the 21st of May, and 

 near each was the shrunken remains of one of the span-worms in which 

 the parasite had lived. One of the parasitic flies issued one week 

 later. It is probable that a Tachina -fly of some kind also attacks these 

 span-worms; on the day above mentioned I found one of them to whose 

 body was attached a white egg 7 evidently of one of these flies, but as 

 no parasite issued from this span-worm I am unable to settle this point 

 at the present time. 



Mr. Cooper informs me that he sprayed some of the infested trees 

 with Buhach and water at the rate of 1 pound to 50 gallons, but this 

 did not destroy the span-worms. He also tried the kerosene emulsion, 

 such as he uses for the destruction of the Black Scale (Lecanium olece) 

 on olive trees, but this was not effectual. Paris green was also used 

 in varying strengths, from 1 pound in 50 gallons to 1 pouud in 200 gal- 

 lons of water, and this latter strength he found effectually destroyed 

 the span-worms without injuring the trees. With each 100 gallons of 

 this mixture he used 20 pounds of a soap made principally of mutton 

 tallow and caustic soda; this caused the solution to spread more 

 readily over the leaves, and also had a tendency to cause the poison-to 

 adhere more firmly. The soap was first dissolved in hot water, after 

 which the Paris green was added, then the balance of the water, and 

 the solution was kept constantly stirred while being applied to the trees. 

 Mr. Cooper informs me that live men — one to drive the team, one to 

 stir the solution in the spraying tank, another to pump, and two to 

 handle the spraying nozzles — sprayed on an average 27 of his largest 

 walnut trees in a day; this is equivalent to one acre of trees per Aax. 



