28 REPORTS OF OBSERVATIONS AND EXPERIMENTS. 



When full grown, these caterpillars crawl into some sheltered place 

 and spin their thin, pure white cocoons. The cocoon proper measures 

 from 18 to 26 mra . in length, and the width is about two-fifths of the 

 length. It is thinly sprinkled with a yellow powder, and around it is 

 spun quite a large quantity of fine, soft, white silk. About four weeks 

 elapse between the spinning of the cocoons and the issuing of the 

 moths, the latter issuing at various hours of the day, from 9 o'clock in 

 the morning to 5 o'clock in the afternoon. The sexes appear to be quite 

 evenly divided; out of a total of 27 moths which I reared, 15 were 

 males and 12 females. 



I did not succeed in breeding internal parasites of any kind from 

 these caterpillars, but they evidently do not altogether escape the 

 attacks of such parasites, since I found two of the caterpillars each of 

 which had a white egg of some kind of Tachina fly attached to its 

 head. This parasite, however, appears to be very rare. Out of a total 

 of 350 of these caterpillars which I examined the two mentioned above 

 were the only ones showing any indication of its attacks; and from 

 about 300 reared not a single parasite made its appearance. 



As stated above, the young caterpillars spin a silken web or tent in 

 which to dwell, and as this is a very conspicuous object, their presence 

 upon the trees may be easily detected and the web with its entire con- 

 tents may then be removed from the tree and burned, or destroyed in 

 some other manner. Later in the season, when the nearly full-grown 

 caterpillars are congregated upon the trunk of the tree they may be 

 destroyed by wrapping a barley sack tightly around the trunk of the 

 tree where they are located, thus crushing them. The method first 

 mentioned is greatly to be preferred, since the white webs of the young 

 caterpillars are much easier to discover than are the caterpillars them- 

 selves, and of course it is far better to destroy them at this time than 

 to wait until they have committed all the injury to the trees that they 

 are capable of doing. 



In a certain locality in Alameda County I found a second species 

 of tent-caterpillar upon cultivated gooseberries, and in a neighboring 

 canyon this same species occurred in large numbers upon wild black- 

 berry (Rubus vitifolhis) and also upon willow. It is readily distin- 

 guished from the one described above by the velvet-black color of 

 its body which is marked with a series of indistinct dull orange yellow 

 dashes that sometimes form two more or less distinct dorsal lines and a 

 lateral line; on either side of each of the segments from the second to 

 the eleventh is a transverse, bluish-gray subdorsal spot; the spiracles 

 and venter are wholly black; the body is thinly clothed with reddish 

 hairs which are most abundant on the back and low down on each side 

 of the body; the head is opaque black, the clypeus gray and bordered 

 below with yellow. The full-grown caterpillar measures about 35 mm 

 in length. The cocoon resembles that of the preceding species but is 

 somewhat darker and more dense, the yellow powder is more abundant, 



