COLEOPTEEOTJS INSECTS. 143 
of the anterior legs. The species figured is about 
nine lines long and five broad. The colour is blu- 
ish black, slightly glossed with purple, and having 
faint coppery reflections ; the whole surface highly 
polished and resplendent. During life the purple 
and blue form pretty distinct bands on the elytra, 
especially towards the sides. The under side of the 
body is pitch brown, the natatory legs paler : the 
fore-legs are very long, and of a brownish-black co- 
lour. It was received from Java. 
Three principal or typical forms prevail among 
beetles of strictly aquatic habits, to one or other of 
which nearly all of them may be regarded as refer- 
rible. Two of these have just been described as 
characterising the families Dytiscidce and Gyrinidce , 
and we shall now proceed to point out the distin- 
guishing marks of the third. Many of the species 
of wdiich it is composed formed a part of the great 
Linnaean genus Dytiscus, but they differ so essenti- 
ally from the insects to which that term is now ap- 
plied, that Latreille, in his systematic arrangement, 
has removed them to a great distance from their 
former associates. Most other ‘naturalists, however, 
have to a certain extent preserved the connection, 
ow'ing to the affinity that arises from their inhabit- 
ing the same element, and presenting some points 
of resemblance in structure. The most striking 
character is the great length of the maxillary palpi, 
which are often considerably longer than the an- 
tennae — a circumstance which has led the group to 
