328 



SCIENC E- G OS SIP. 



etc., where the smooth type of female is more 

 generally abundant and of a brighter green colora- 

 tion. In Britain the species is decidedly uncommon, 

 and confined chiefly to the London district. 



Dytistus eiri-v mci actus Ahr. (fig. 11) is less 

 variable in size than is our commonest species, to 

 which it bears a strong resemblance. It measure^ 

 about one and a quarter inches in length and five- 

 eighths of an inch in breadth (31-33 mm. by 

 15-16 mm.). The colour of the upper surface i.< 

 screenish-black, with the wing-cases and thorax 

 bordered as in the last two species : antennae and 

 legs red. From D. marginalis it may be distin- 

 guished by having the coxal processes more 

 elongate and sharp, and from J), .drcumflexus by 

 the absence of the black markings on the underside, 

 whilst it differs from both of these species in having 

 a narrow yellow border round the eyes. The sexes 

 differ as in D. marginalis, the males being glabrous 

 and the females dimorphous, either dull and sul- 

 cata, or smooth and polished, but with more 

 punctuation towards the apex of the elytra than 

 the males. 



This insect is a native of Xorth-East Europe and 

 North America. In Britain it is decidedly rare, but 

 the fact of its having been recorded from localities 

 as widely separated as Eastbourne, the Cambridge- 

 shire fens, and Askham Bog near York (" Col. Brit. 

 Is."), should stimulate ardent coleopterists to en- 

 deavour to locate it in intermediate districts. 



Dytiscm lapponicus Gyll. (fig. 13) is one of our 

 smaller species. Although very variable, its general 

 average size is scarcely so large as that of I). pttne- 

 tulattis (23-28 mm. by 12-15 mm.). In form it is 

 slightly more oval than the latter beetle, and on 

 account of the thorax being narrower in propor- 

 tion, especially at the base, the general outline of 

 the insect is less continuous than that of any of 

 our other species. The colour of the upper surface 

 is pitchy or blackish-brown ; the fact that the 

 elytra are finely striped with longitudinal yellow 

 lines also imparts to the beetles a generally 

 lighter appearance than is presented by other 

 members of the genus. The underside is 

 yellow with black markings along the lateral 

 edges (fig. 13). the coxal processes being long 

 and sharp. This species may be distinguished 

 from I), marginalis and I). circumflex a* by the 

 broad yellow border round the eyes, and from 

 D. circumcinctus by the black markings on the 

 abdomen. The males are smooth and shining, with 

 the elytra punctured towards their apex, the 

 females being, as a rule, dull and deeply furrowed, 

 although occasionally resembling the stronger' sex. 

 D.loppnri Ht extends from Central Russia and 

 Germany throughout Northern Europe and Siberia. 

 With us it is a very local insect, and confined for 

 the most part to the Highlands of Scotland and 

 Ireland. Yet. although usually a scarce insect, it 

 - not infrequently occurred to collectors in con- 

 siderable quantity. Mr. James J. F. X. King, of 



Glasgow, to whom I am indebted for my British 

 specimens, obtained it in Mull in September 1S9'.» 

 in great number. 



Dgtiscus dimidiatus Berg. (fig. 14) is the last and 

 largest of our indigenous species. It ranges in 

 size from one and a quarter to one and a half 

 inches in length, whilst attaining a breadth of 

 about three-quarters of an inch at the broadest 

 part of the elytra (32-37 mm. by 17-18 mm.), which 

 is situated rather farther back towards the apex in 

 this than in others of the genus. The upper side 

 is pitchy-black : the antennae and legs red ; and 

 coxal processes blunt. The underside is somewhat 

 darker, and exhibits a more ruddy appearance than 

 in any of the preceding insects. Jj. dimidiatus 

 differs from the rest of the group in having only 

 the side margins of the thorax broadly bordered 

 with yellow, a narrow streak being also traceable 

 along the anterior edge. Like D. pmwtulatus, the 

 females of this species exhibit but one form, being 

 always deeply silicate from near the base to just 

 beyond the middle of the elytra ; the males, as in 

 the other species, being smooth and polished. 



I), dimidiatus occurs on the Continent and in 

 Asia Minor, and was formerly plentiful in the fen 

 districts of England : but, notwithstanding that a 

 recently published encyclopaedia brackets it with 

 D. marginalis as one of our two commonest British 

 species, there is little doubt that this beetle is now 

 by far the rarest of our indigenous Dytisci, and 

 bids fair to occupy a place ere long in the growing 

 list of our extinct insect fauna. 



The Dytisci are easily kept in captivity, and 

 make interesting pets, becoming in time so tame 

 that they do not appear to mind being lifted out of 

 the water and examined in the hand. In their 

 natural element their movements are varied and 

 marked by extreme gracefulness : whilst at times. 

 particularly in some of the cat-like methods of 

 cleaning themselves, their performances become 

 amusingly grotesque. The naturalist who is pos- 

 sessed of an aquarium, or who is sufficiently handy 

 with his tools to fabricate one after the manner 

 described in an early number of Science-Gossip . 

 (January 1886). will find much to learn from a 

 study of the habits and actions of these interesting 

 insects. Especially will this be so if able to 

 arrange a bath or other large receptacle for water, a- 

 previously described {ante. p. 326). so as to give the 

 beetles ample room and opportunity to display 

 themselves to advantage. Then they will be found 

 to prove much more instructive and educating 

 than goldfish, or the generality of the usual occu- 

 pants of our private aquaria. 

 Saxholme, Moyldke. 



•■ The Caiibbian X atcral Observer " for 

 January and February 1901 is to hand, and con- 

 tains much that is interesting, including a history 

 of the Astronomical Society of Wales, of which it 

 is the organ. The Society appears to be making 

 good progress. 



