EXPERIMENTS IN PREVENTION OF EMERGENCE 31 



only about fifteen per cent of the egg-masses were exposed. 

 The ploughing occurred about a week before emergence and 

 so had no appreciable effect upon the hatching of the eggs. 

 It is possible that, could ploughing be done a month or so 

 earlier and could it be accompanied by a breaking up of 

 the clods and an exposure of broken egg-masses, good 

 might be done. It seems doubtful whether the work could 

 be done sufficiently thoroLighly to give results commensu- 

 rate with the labour expended. 



Deep ploughing to bury the egg-masses has not, as 

 yet, been tested. However, experiments have been carried 

 out to ascertain through how many inches of soil the freshly- 

 hatched hoppers are able to work their way upward. The 

 different power of different species of grasshoppers in this 

 respect is quite remarkable. Eiley^ reports the results of 

 experiments on the power of emergence of newly- hatched 

 hoppers of the Rocky Mountain Locust, which show that 

 they do not usually make their way up through more than 

 two inches of soil, though they occasionally may do so. 

 A still weaker power has been observed by the senior 

 author for the Jola Grasshopper {ColemcDiia splienarioifles, 

 Bol), the record of which will be published shortly.'^ 



The results obtained in experimentii on the Rice 

 (J-rasshopper are quite different from those already men- 

 tioned. Two series of experiments were carried out, which 

 show quite conclusively that freshly- hatched Rice Grass- 

 hoppers are able to tunnel their way up through at least 

 six inches of fairly well compacted soil. 



In the first set of experiments, two egg-masses were 

 buried upright, at a depth of five and six inches respectively, 

 in two glass tubes filled with fairly compact but rather light 

 soil. In each case, all the eggs hatched, and all the 

 hoppers made then- escape to the surface through a com- 

 mon somewhat tortuous tunnel, made in the soil close to 

 the wall of the tube. Plate II, Fig. 3 is reproduced from a 

 photograph of one of these tubes made during the 

 emergence. Only about half the burrow is visible, the 

 lower part curving off out of sight to the right. Two 

 nymphs are to be made out close together in the burrow 

 and one of these has already shed the amnion. 



1 Riley, loc. cit., p. 356. 



- Coleman, The Jola or Deccan Grasshopper, Mysore Agricultural Department, 

 Entomological Series, Bulletin No. 2, 1911, already published, 



