DISPERSAL OF SHELLS BY BEETLES. 

 By Rev. E. P. Blackburn. 



EARLY in August, 1903, a small party of conchologists 

 visited Tibthorpe Wold, to the west of Driffield. 

 Near Mr. Piercy's farm-house, at a height of nearly 

 400 feet, is a pond, the nearest water to which is half a 

 mile away, and the next a mile away. It has been in use 

 for some time, but, in common with other ponds on Sir 

 Tatton Sykes' estate, is frequently cleaned out, and conse- 

 quently did not appear very productive from a conchologist's 

 point of view. About six years ago it was entirely emptied 

 and re-lined. Application of the scoop, however, quickly 

 brought up a host of Pisidia, with which the pond swarmed 

 on one side, together with a number of small water-beetles, 

 water-boatmen, and water-bugs. A few Limncea peregra 

 were put in the pond a year ago, but had not survived for 

 want of food. Several of the beetles were observed with 

 something on their feet in the pond, but it could not 

 exactly be seen what. The pisidia were brought home, and 

 put in a basin with their native mud, and it was found that 

 a number of water-bugs (Corixa) and beetles had been 

 brought along with them. The next day we saw a bug 

 (Corixa) in the bowl caught by the foot with a pisidium. A 

 day or two later I was examining the contents of the bowl, 

 and found three others caught. I killed the insects, and 

 gummed them on a piece of paper. No. 1 had two pisidia 

 on two back legs. No. 2 had three shells attached ; one a 

 fairly large one. No. 3 is more perfect, and has two shells, 

 one on each side. Two days later, I found a lively little 

 water-beetle caught, but he managed to get free. A 

 fourth specimen, however, was secured with one pisidium 

 attached. Wallis Kew (in "The Dispersal of Shells "), after 

 explaining how ponds, similar to the above, are stocked with 

 pisidia by means of flying insects, animals, &c, says : "Some 

 of our common water-boatmen are, probably, even stronger 

 than the Nepa, or water-scorpion. I have, once or twice, 

 seen them alight upon the surface of the ponds, in the sun- 

 shine, fold their wings, and disappear in the water." With 

 the specimens above mentioned, it is quite plain that ponds 

 may be stocked very easily in the way described. 



