On Aquatic (xirnivorous Coleoptera or Dytiscidos. 747 



Group 6. 



1169. Dytiscus rceselii, Fab., Tragus virens, 31. C. — Ovalis, postei'ius conspicue 

 latior, supra olivaceus, capite anterius prothoraceque lateribus testaceis, elytris vitta 

 lateral! versus apicem attenuata, et a margine laterali separata, testacea ; corpore 

 subtus testaceo, pectore in medio plus minusve brunneo, tarsis iutermediis et tibiis 

 tarsisque posterioribus piceis ; femoribus posterioribus angulo externo acuto, 

 subspinoso. Long. 34, lat. 18j m.m. 



The male has the daws on the intermediate feet a good deal longer than in the 

 female, and unequal, the front one being much thicker and a little longer than tlie 

 other; it has the uppersurfaee of the body smooth and shining, while in the 

 female the thorax is covered with curved irregular depressions or scratches, and 

 the wing-cases bear longitudinal scratches which anastomose here and there, a space 

 at the apex remains, however, always smooth. On the undersurface the epipleurse 

 of the female are conspicuously flattened just behind the shoulder, while at the 

 same spot they are rounded in the male. 



In this species the yellow band of the elytra at the shoulder starts from quite the 

 outer margin, but becomes thinner towards the extremity, and is in a gradual 

 manner more and more separated from the outer margin,itbecomes quite obsolete be- 

 fore the apex, but at the apex the external margin is itself vaguely yellow, and the ex- 

 tremity of the yellow band is only separated in a very vague manner from this terminal 

 yellow colour. The colour of the undersurface varies somewhat, the infuscation of the 

 breast along the middle being sometimes very slight, while at other times it is quite 

 conspicuous, and when it is greatest the coxal processes become quite greenish or 

 olivaceous in colour. The most remarkable variety, however, is one found in 

 Portugal, it is of small size, being about 31 m.m. long, and the sexual characters 

 differ remarkably from what is usual in the species, the female being quite smooth 

 on the uppersurfaee, and the anterior tarsi of the male are unusually small, attain- 

 ing only 21 m.m. in the transverse direction, the normal dimension being 3i m.m. 

 This variety may be designated as var. lusitanicus, I have seen only three individuals 

 of it, two females and one male found by d'Oliveira, it is worthy of remark that the 

 intermediate tarsus on the left leg of the male is like that of a female, while the 

 right foot is normal. 



The species does not extend its range to Britain or Scandinavia. The smooth 

 variety of the female seems very rare, the only specimens T have seen of it come 

 from Portugal. 



Cybister chaudoiri, Hoch., was founded on two females found at Lenkoran, and 

 from the description and remarks of its describer it seems highly probable that it 

 is a variety of Dytiscus rceselii. 



Europe and Northern Africa. Northern France, Belgium, Germany, Portugal, Corsica, Italy, Greece, 

 Corfu, Siberia, (East India ?) 



TKANS ROY. DUB. SOC, M.S., VOL. n. 8 D 



