262 



SCIEA r CE-GOSSIP. 



BRITISH DUMBLE-DORS. 



By E. J. Burgess Sopp, F.E.S. 



(Cotu:litded/roi/i page 227.) 



"CPOR convenience we may divide our dumble-dors 

 into three groups. 



Geotrupes lyphaeus, the only representative of our 

 first division, is of aunicolorous shining black, although 

 specimens are occasionally met with exhibiting a rich 

 dark brown hue, which may however probably be 

 attributed to immaturity. The species varies much 

 in size, individuals ranging from three- to nearly 

 seven-eighths of an inch in length. The sexes differ 

 considerably in appearance, the front of the thorax 

 in the male being armed with three pointed horns 

 which project forwards, one over and the others at 

 either side of the head. These formidable-looking 

 weapons vary in length in individual beetles, in some 

 instances being little more than rudimentary promi- 

 nences, whilst in others the exterior spines, which 

 curve slightly inwards, attain to considerably over a 

 quarter of an inch. In the female two tubercles 

 take the place of these outer spines, between which 

 runs a well-marked raised ridge. The nature of the 

 sculpture of the pro-thorax alone serves to easily 

 distinguish G. typliaens from all other species of the 

 genus in which the thorax is without raised pro- 

 minences of any kind. In the Fabrician arrange- 

 ment of Coleoptera, this beetle, together with several 

 of the following species, was placed in the genus 

 Scarabaeus. G. typhaeus is locally common in the 

 Midland and Southern Counties of England, but 

 becomes much scarcer farther north. It has been 

 recorded from several places in Ireland, but does 

 not appear to occur in the extreme North of England 

 or in Scotland. 



Our second group comprises three beetles which 

 constitute our largest British dumble-dors. Of these 

 the first and second are extremely alike and 

 invariably present difficulties of separation to the 

 young coleopterist. 



Geotrupes spiniger is an oblong-oval beetle, of from 

 five- to seven-eighths of an inch long. The upper 

 side is black and often dull, the under parts very 

 shining by comparison, and of a violet, blue, green, 

 or bronze metallic coloration. The sides of the 

 thorax are closely punctured, the markings becoming 

 much more spread out upon the disc, across the 

 centre of which can be traced a longitudinal line with 

 a double or single row of pits or larger punctures. 

 These markings on the disc however are not constant, 

 and vary in distinctness in different beetles. By the 

 aid of an ordinary magnifying glass it will be seen 

 that with one exception the under surface of the 

 insect is closely punctured and thickly covered with a 

 quantity of hairs. The exception is a space lying 

 along the centre of the abdomen where there runs 



lengthways a smooth bare band, both impunctate and 

 devoid of pubescence. The presence of this distin- 

 guishing mark is much more easily seen in some 

 specimens than in others, when it is sometimes a 

 little difficult to make out with satisfaction. It is 

 however a point of great importance in the differentia- 

 tion of the species and must therefore be specially 

 sought and noted. G. spiniger is one of our com- 

 monest beetles, and is widely and generally 

 distributed throughout the kingdom. 



Geotrupes stercorarius, the giant of the genus, 

 occasionally attains to the length of an inch. It is 

 exceedingly like the last-named beetle, but exhibits 

 as a rule a fresher and more polished appearance. 

 The thorax is much less punctured than in spiniget 

 and the central line on disc less evident. The chief 

 distinguishing point lies in the absence of the central 

 smooth bare longitudinal space beneath, the under- 

 side of the beetle being punctured and pubescent 

 throughout. Kirby mentions that the bright 

 polished thighs of this and others of the genus are 

 strung on strings and worn as necklaces by women in 

 various parts of Europe. Although perhaps not 

 quite so common as the preceding insect, G. sterco- 

 rarius is nevertheless widely distributed over the 

 British Islands. 



Geotrupes mutator ranges almost as large as our last 

 beetle, to which it bears a certain resemblance, but 

 as a rule the colouring of the upper surface is much 

 brighter than in either of the other members of the 

 group, in which the tints rarely pass beyond blue- 

 black or black-violaceous, whereas in G. mutator they 

 often assume a rich violet, green, purple, or bronze 

 metallic shade. The species is readily known from 

 all our other dumble-dors by the fact of its having 

 nine striae between the humeral prominence and 

 sutural margin of each elytron, whereas the other 

 members of the genus possess but seven. G. mutator 

 is a decidedly local beetle and seems to be only found 

 in somewhat restricted areas in the Southern and Mid- 

 Southern Counties of England and in South Wales. 

 It has not apparently occurred in the North of 

 England, nor has it been recorded from Scotland or 

 Ireland. 



The members of our third and last group are very 

 similar in appearance. They are distinguished from 

 G. typhaeus by the absence of tubercles or horns, 

 and from the beetles constituting our second division 

 by their average smaller size and short oval, less 

 oblong, form. In addition to being dung feeders, 

 the insects belonging to this group are not infre- 

 quently found in decaying fungi and like situations. 

 Geotrupes sylvaticus often runs slightly larger than 



