MEANS OF DISTRIBUTION. 57 



The local spread of the insect from orchard to orchard and from 

 tree to tree must also be brought about thru the agenc}^ of means 

 other than those under the control of the insect itself. The female is 

 wing-less and after once becoming fixt can not move. The young lice, 

 as before stated, are active, crawl rapidly, and ma}^ reach other trees, 

 but this is rare unless the limbs interlace, since we have shown by 

 breeding-cage experiments that the larvse normall}^ crawl but a few 

 inches. Such spread, however, is comparative! 3^^ insignificant except 

 in the case of nursery stock, which is grown close together. It is 

 possible that strong winds may carry the young bodily from one tree 

 to another, or the}^ may be floated on water to distant points, particu- 

 larly in irrigated districts, but the principal method of the spread of 

 these young lice is by means of other insects and by birds. The active 

 young lice soon crawl upon any small winged insect, particularly if 

 the latter be of a dark color, and ma}^ thus be carried considerable 

 distances. They are frequently found crawling upon ants, which are 

 great travelers. It is extremely probable that they also crawl upon 

 the feet of birds, and ma}^ be transported by these carriers for many 

 miles. 



Some interesting observations have been made by Mr. Schwarz upon 

 the transporting of these scale larvae by other insects. A little black 

 ladybird, Microweisea {Pentilia) misella Lee, which was very active 

 in devouring scale larvae, was unfortunately equally efficient in trans- 

 porting many of these young lice to other parts of the tree or to other 

 trees; in fact, it was difficult to find a single beetle which did not carry 

 on its back at least one larva of the San Jose scale, and sometimes three 

 or four were found upon a single wing cover of a beetle. The small 

 black ant, Monoinorium minutuin Mayr, was /particularly abundant 

 upon pears, attracted by the juices emerging from cracks, and almost 

 every one of these insects carried on its back one or more specimens 

 of the young scale insects. Specimens of the little chrysomelid beetle 

 Typophonis canellus Fab. were also found upon the trees. Both red 

 and black specimens of this beetle occurred, and the interesting obser- 

 vation was made that while Aspidiotus larvae crawled freely on the 

 black individuals, no specimens were to be found upon the red ones. 

 The same peculiarity was found to hold true with the ants. The red 

 ant, Fonnica schaufussi Ma}^', was abundant upon the pears, but no 

 specimens were found bearing Aspidiotus larvae, while, as just stated, 

 the little black Monomorium was always found carrying them. 



As illustrating this transportation of the scale by birds or insects 

 the experience at Riverside, Md. (Bui. 3, p. 25), may be cited, and 

 Professor Smith reports a similar instance in New Jerse}^, in letter of 

 January 13, 1896. 



In spite of the abundance of insects which may transport the larvae 

 the progress of the scale from infested trees to noninf ested trees is 



