METHODS OP SPREAD 



S9 



Methods of Spread. 



As already noted, the young, after hatching, generally 

 do not fix themselves mimediately, but wander about for 

 some time. The movements are very slow and progress 

 varies with the kind of surface. On the under side of 

 leaves the movement is quickest. On loose, fine soil it is 

 much slower, and still more so on moist soil. The follow- 

 ing table gives an idea of the rate of progress of newly- 

 hatched nymphs on various surfaces : — 



Date 



Time taken by 

 the nymph to 

 walk over the 

 distance 



Distance gone 

 over 



Condition of the 

 surface over 

 which the bug 

 travelled 



Remarks 



19th March, 

 1917, 



16th March, 

 1917. 



21st March, 

 1917. 



23rd March, 

 1917. 



21st April, 

 1917. 



2 hours (11-30 A.M. 

 to 1-30 P.M.) 



2 hours (1 P.M. 

 to 3 P.M.) 



2 hours (11-15 A.M. 

 to 1-15 P.M.) 



2 houi's (12 noon 

 to 2 p.m.) 



Do 



164 inches 



7 



U „ 

 30 



Black glazed 

 paper. 



Black sand paper 



Ordinary paper 

 smeared over 

 with fine mud 

 and dried. 



Same as above 

 but moist. 



Coffee leaf 



The nymph stop- 

 ped for five 

 minutes in one 

 place. 



Bug stopped now 

 and then and 

 had frequently 

 to be forced to 



Young green bugs removed from leaves and kept in^ 

 glass dishes, where they had no opportunity of feeding, 

 were found not to live longer than four days. Under 

 more natural conditions, life without food may be longer, 

 but even so it seems improbable that young bugs can* 

 move far enough of their own accord to contribute largely 

 to the spread of the pest in coffee estates. 



It has been recentl}^ proved^ that winds blow the 

 young scale insects from their host plants to distances up 

 to 450 feet, the longest distance for which the ex- 

 periment was tried. The older bugs also do not always 

 remain fixed. The movements after moulting have already 

 been mentioned, and there is additional inducement for 

 movement when the leaves are overcrowded and nutrition 

 becomes insufficient. 



The disturbances so caused may be so great that a 



* H. T. Quayle, Dispersion of Scale Insects by the Wind. Jour. 

 Ec. Ent. Vol T. p. 48G. 



