226 



THE BRITISH NATURALIST. [November 



the following in reference to the same. ater, nearly inches in 



length,- blackish, sides lighter, yellowish fringe," It is now, 6th 

 October, back black, with scarcely a trace of yellow in the foot 

 fringe, sides blackish, in fact the ordinary black form. 



In respect to A . ater, I noted a year or so ago a curious fact of which 

 1 published the particulars elsewhere. A couple, one black the other 

 light drab, paired in one of my cases, the black deposited eggs, many 

 of which hatched, and all of which resembled the other parent in color, 

 being however rather lighter at first, and developing lateral lines of a 

 slightly darker hue in about a monih. These disappeared later through 

 a gradual and slight darkening of the whole upper surface of the 

 animal. I was not aware till that time that A. ater was banded in 

 youth and was doubtful whether this banding would or would not be 

 found in the black variety, however the notes previously given show 

 that this also has lateral lines at an early period." 



I have been led by my observations to the conclusion that the 

 greatest enemies of our terrestrial moUusca are the larvce of smal| 

 Dipera, of at least two species. From tiie commencement of my 

 breeding experiments I had observed a number of little black flies, not 

 unlike those produced by the cheese hopper, they are so small as to be 

 able to get through the holes in the perforated zinc with which my 

 pots are covered, in time large numbers of larv(v are produced which 

 prey on the eggs of the slugs and snails, I have frequently had a fine 

 batch of eggs from which I was hoping to gee a good supply of young 

 mc Husks, when on the next inspection their place has been occupied 

 by a few fragments of the outer portions — shells of the eggs, and a 

 wriggling mass of these, to me, pests. My notes describing them are 

 as follow: 6t]"> September, 18S9, "Eggs oi A . suhfuscu:^ ^di\e gxeen — 

 other eggs of this specie.s are described as becoming yellowish." 30th 

 November, "Eggs disappeared, in their place Dipterous larvce, trans- 

 lucent, from l to ^- inch in length." 5th November, "These larva 

 extended i inch, fine as a hair." Bth November, 1890, "A number of 

 larva appeared . . . the greater part of the eggs' destroyed. These 

 Inrvcp. are |- an inch in length, broader than those previously observed, 

 quite white and transparent as glass, the intestinal canal clearly seen 

 as a brown streak, heads shining black." 



* Since writing the above I have read the article on this species in Dr. R. F. 

 Scharff's admirable treatise on " The Slugs of Ireland," published in the transactions 

 of the Royal Dublin Society for the present year, in which this fact is fully recognised. 



