27 



ago there were but few signs, now the whole tiling is being eaten op. I nerei 

 anything so ravenous. Please write me at once what to do and what it i-. I 

 the crop is gone.— EiJLWOOD COOPEB. 



Thinking- the matter of sufficient importance to require investigating, 

 I paid ii visit to Mr. Cooper soon after the middle of May. Prior to 

 this, however, the trees had been sprayed with Paris green and water 



at the rate of 1 pound of Paris green to 130 gallons of water, and now 

 it was no easy matter to find any li dug, healthy worms. The trees at- 

 tacked were very large ones, being about 30 feet high, and the branches 



extending a distance of nearly 20 feet, making for the tops of the trees 

 a diameter approximating 40 feet. The span-worms appeared upon 

 nearly every tree in a grove containing 20 acres, but they were most 

 abundant near the center of the grove, where they had almost com- 

 pletely defoliated the trees. They also appeared upon the walnut trees 

 in an adjacent grove, but not in such large numbers as in the one above 

 mentioned. Mr. Cooper informed me that he has lived on this ranch 

 continuously for nineteen years, but never before had these or any 

 other kind of span-worms appeared upon his trees in sufficient num- 

 bers to attract attention, and he is unable to account for the present in- 

 vasion. 



The following year these span-worms were also present upon some 

 of the trees, but were far less numerous than during the preceding 

 year. The infested trees were again sprayed with Paris green and 

 water at the rate of 1 pound to 180 gallons, and this effectually de- 

 stroyed the span-worms. In the month of March of the present year, 

 however, Mr. Cooper wrote me that the span-worms were again appear- 

 ing in large numbers and requested me to come to his ranch and inves- 

 tigate them. Having received instructions from Dr. Riley to this ef- 

 fect, I again, on the Gth of April, visited Mr. Cooper, and found that, 

 while the span-worms were quite abundant upon some of the trees, still 

 they were in much smaller numbers than during the season of 1890. I 

 also made a careful examination of the trees growing near the walnut 

 trees; these consisted of Olive, Persimmon, Eucalyptus, Sycamore, Al- 

 der, Oak, Elder, Willow, and a few other kinds of trees, besides various 

 kinds of shrubs and plants, but failed to find specimens of this span- 

 worm upon any of them, with the single exception of the Oak (Querent 

 agrifolia). The new, spring growth was just starting out upon this 

 tree, and I found several of these span-worms feeding upon the new ly 

 expanded oak leaves; a careful comparison of these oak-feeding speci- 

 mens with those from the walnut trees failed to disclose the slightest 

 difference, and when I tested them with walnut leaves they also fed 

 readily upon them. Several trees of black walnuts are also growing on 

 Mr. Cooper's ranch, but these were not yet in leaf at the time o( my 

 visit. 



During a visit which 1 made, in the latter part of April, to portions 

 of Alameda and Santa Clara counties 1 found specimens of this same 



