Uequhart. — On the Work of Earth-worms. 119 



Aet. XI. — On the Work of Earth-worms in New Zealatid. 



By a. T. Urquhakt. 



[Read before the Auckland Institute, lith November, 1886.] 



Although it has become generally known, since the publi- 

 cation of Mr. Darwin's researches, how rapidly surface debris 

 is buried through the action of earth-worms, the result of 

 a few observations may, nevertheless, be worth recording, 

 as they afford means of comparison between the work done 

 by the New Zealand and the British species. The compara- 

 tive weight of their castings, and an estimate of the number 

 of earth-worms usually found in some of the cultivated and 

 uncultivated lands in Auckland District were given in a lormer 

 paper, " On the Habits of Earth-worms in New Zealand. "='' 



A section was described, the result of the work of worms, 

 chiefly the common Lumbricus campestris, but only an approxi- 

 mate estimate could be arrived at as to the length of time 

 which it had taken for the surface - charred debris to sink 

 to an average depth of about 5f inches. The section when 

 first exposed, in 1875, showed an average of 4^ inches of 

 black vegetable mould, free from stones, etc., and a horizontal 

 layer, nearly 1 inch thick, of charred wood, burnt marl, 

 fragments of jasper, and pumice, lying on tbe subsoil, a 

 brownish-green arenaceous clay. In October, 1883, [i.e., in 

 eight years,) the depth of mould had increased 1^ inches, 

 giving an average depth of about 5f inches above the burnt 

 layer ; during the past three years there has been an even 

 average increase to the superficial layer of nearly 1 inch, 

 the total depth now being rather more than 6J inches. 



Considermg the depth of vegetable mould above the charred 

 layer, this certainly appears to be a considerable increase 

 for so short a period, but apparently the estimate is correct : 

 it is in all probability to be attributed, independently of 

 the increase of worms since the land has been in grass, to 

 the moisture and nature of the subsoil. Worms living in 

 lands with a moist substratum continue to work at a low 

 level, not only during the short intervals of dry weather 

 that occur in the spring months, but as long as there is 

 sufficient moisture ; whereas in the upper lands, during these 

 di'y intervals, the worms cease to work, retire temporarily 

 to their chambers, coil themselves up, and remain apparently 

 in a dormant state until rain sets in again. 



On the 15th October, 1883, a layer of charred wood and broken 



* " Trans. N.Z. Inst.," vol. xvi., 1883, p. 266. 



