REPORT OF THE ENTOMOLOGIST AXD BOTANIST. 



209 



elongated shape. The legs and feelers have appeared again, and there are now promi- 

 nent wing pads extending along the sides of the body. About twenty days after birth 

 the male insect changes to the true pupa, in which all the parts shown in the pro-pupa 

 are much more developed, and a slender organ at the end of the body called the style 

 has appeared. From four to six days later, or from twenty-four to twenty-six days after 

 birth, the males mature and emerge by backing out from the rear ends of their scales; this 

 is chiefly by night or in the evening. 



The changes which have gone on beneath the female scale are less striking than 

 those described above. After the first moult the body of the female is practically an 



almost circular, flattened sac, with 

 indistinct segmentation and with- 

 out any visible organs, except the 

 long sucking bristle with which it 

 draws up continuously the sap of 

 the tree it is infesting. The female 

 ^ mim ?-^7V^^ *f7wr^ ^xc^'^yf mm. moults a second time about 20 



6- r i^SIV^^^^^^Ml^li (?) days after birth, and the last seg- 



^ ment now shows the important 

 characters of the mature female, 

 which are of so much service in 

 the exact identification of the spe- 

 cies. The segmentation of the 

 body at this stage is quite distinct. 



Thirty days from birth the 

 females are full grown and the em- 

 bryonic young may be seen within 

 their bodies. The mature female, 

 prior to the development of the 

 young, is -^jj of an inch wide by -^ 

 of an inch long. The length of 

 time necessary for the development 

 of a generation varies somewhat ; 

 according to the Washington ob- 

 servations, it covers a period of from 33 to 40 days from the time a young larva appears 

 until it develops into a mature female bearing young. The San Jose Scale is enormously 

 prolific. It has been calculated that a single female may be the progenitor of 3,216 

 million descendants in a single season. 



The exact identification of the species is of the greatest importance, for the San 

 Jos^ Scale is now known to have many very bad characteristics not possessed by several 

 other scales which resemble it very closely in appearance ; and these make it a matter _ 

 of public interest that no efibrt should be spared to control so dangerous a public enemy 

 whenever it is detected in a new locality. The chief differences, in this connection, 

 between the San Josd and some of these other scales are : (1) the fatal effects on the tree 

 due to its greater rapidity of increase, and (2) certain minute but important structural 

 characters which can be seen only with the help of a microscope. 



The careful experiments at Washington, already alluded to, show that in one 

 season from a single female an increase of 3,216 millions is possible. It is not, of course, 

 to be expected that all of these would survive ; but with the San Jos^ Scale there are 

 many circumstances which make it less liable to diminution than many other insects. 

 As a matter of fact, it is known that this scale does not spread from a new point of 

 infestation with very great rapidity to contiguous trees, and also that, when once estab- 

 lished upon a tree, it soon increases enormously in numbers — indeed, unless checked, 

 usually spreading rapidly over the whole tree and destroying it. This rapid increase is 

 characteristic of the species and is due, of course, to the great fecundity of the females. 

 The fact that they bring forth their young alive throughout the season and that these 

 are very quickly protected by a scale which is impervious to many liquids, affects very 



14 



Fig. 18.— San Jos^ Scale. 



(6.) Scale much enlarged, (c.) Female showing young, 



much enlarged, {d.) Anal lobes of female. 



