91 



ON GEOTRUPES STERCORARIUS AND ONE OF ITS 

 PARASITES. 



By T. a. chapman, M.D. 



You are all doubtless well acquainted with the largest subject of the obser- 

 vations I propose to lay before you, viz., the "the shard-born beetle with its 

 drowsy hum " of the poet — the Geotrupes stercorarius. Some five years ago 

 I was struck by the fact that, notwithstanding that this is one of our com- 

 monest and largest native beetles, I could find no satisfactory account of its 

 life history in any work accessible to me, and those remarks that did appear 

 were very vague, and where definite were, as I afterwards found, frequently 

 inaccurate. I determined, therefore, to observe the creature for myself, and 

 was rewarded in doing so by finding that another beetle of the same lameUi- 

 come family was attached to it as a cuckoo jjarasite ; this fact is very remark- 

 able, as all the beetles of this family are not only vegetable feeders, but are all 

 supposed to be of most pacific and unaggressive habits. This other beetle is the 

 Aphodius porcus. 



The principal facts of the history are to be observed in Seiitember and 

 October, and, indeed, throughout the winter. In these months almost any 

 horse or cow dropping may be observed to have one or several small heaps of 

 mould beside it ; these are the result of the excavations beneath by Geotrupes 

 stercorarius, and by raising a considerable jjiece of turf with care all the facts 

 I am about to relate may be observed. 



Single specimens of Geotrupes stercorarius may be found in short burrows 

 under horse or cow droppings, but when the business of oviposition is com- 

 menced a pair of beetles are always associated. The burrow, formed with this 

 object, extends nearly vertically downwards to a depth of six to eight, or even 

 twelve inches, and as many as five or six pairs of beetles are sometimes at work 

 under one dropping. This vertical burrow is almost always made without any 

 excavation, simply by the thrusting of the earth to one side as the beetle forces 

 its way down. It often haj^pens that when the mouth of this burrow is beneath 

 the centre of the dropping, this opening is kept free for the sujjply of pabulum, 

 and a sabsidiaiy canal is carried thence along the surface of the ground to the 

 edge of the dropping by means of which the earth removed from the deeper 

 workings is ejected. The cavities wherein the eggs are laid branch horizon- 

 tally from the bottom of the jjerpendicular burrow in various directions and at 

 slightly varying heights, to the number of 6 or 8. They appear to be made 

 successively one at a time, the lower being made last. Each Isranch is about 



