DISTRIBUTION BY MAN. 113 



railroad leading out of Boston on which other caterpillars 

 might be carried out. Thus, though many caterpillars might 

 be accidentally carried to a long distance outside the infested 

 region, there was very little probability that any number of 

 such individuals would be dropped within half a mile of each 

 other. Furthermore, the chances that isolated caterpillars 

 would complete their transformations and emerge as perfect 

 insects are very small. Therefore, there would be hardly a 

 possibility of a colony being started by the accidental trans- 

 portation of caterpillars to a distance unless it should be 

 proved that parthenogenesis (the reproduction of the species 

 by the virgin female) occurs.* If, however, the moths should 

 at any time become abnormally numerous on the line of an 

 extended railway, their chances of accidental distribution by 

 regular and constant travel would greatly increase and a 

 wide dissemination would almost certainly follow. So far, 

 notwithstanding the unhindered carriage of caterpillars in 

 this way on the Medford branch railroad for several years 

 previous to 1892, no evidence of the moths' existence at a 

 distance from the infested towns has ever been found along 

 the lines of other railroads. 



THE EFFECT OF THE WORK OF EXTERMINATION ON THE 

 DISTRIBUTION OF THE MOTH. 



"While the work of destroying the gypsy moth has much 

 reduced the numbers of the moths and the extent of territory 

 occupied by them, it has been necessary to exercise great care 

 to avoid accidental distribution of the caterpillars by the 

 workmen. 



The work of spraying is responsible for some slight local 

 scattering of the caterpillars. When the branches of a tree are 

 disturbed by the sprayers, many of the caterpillars spin down 

 and either fall to the ground or are carried about upon the 

 clothing of the workmen or others passing beneath the tree. 

 Unless great care is taken they may be carried from place to 

 place on the spraying team. Those falling to the ground 



* Observations so far made in this country have not revealed a case of partheno- 

 genesis in this species, but, on the contrary, many instances have shown isolation 

 to result in extermination. A few European instances of parthenogenesis have been 

 recorded. 



