The Dyticidce, although inhabiting a different element to 
the CarabidcE , are closely allied to them in structure, par- 
ticularly in the form of the antennae and the organs of man- 
ducation, the maxillae being furnished with 2 pair of palpi; 
and the anterior tarsi are commonly dilated in the males. 
The genus Acilius , established by Dr. Leach in the Zoologi- 
cal Miscellany , may be distinguished from Dyticus by the great 
flatness of the insects, by the hairy elytra of the females, which 
have but few striae, and by the basal joints of the tarsi in the 
2nd pair of legs not being dilated ; the instrumenta cibaria 
also vary particularly in the form of the mentum, and the ter- 
minal joint of the external maxillary palpus, which is longer 
than the penultimate, and thickest in the middle. 
Our insect appearing upon a careful examination to be un- 
noticed by any author we have been able to consult, and being 
darker than the common species, the specific name of caligi- 
nosus has been thought applicable. It has been ascertained 
to be British by Mr. Chant, who, with his friend Mr. Bentley, 
took it plentifully in the ditches at Whittlesea Meer, Hunting- 
donshire, the end of July 1824. It is smaller and darker than 
A . sulcatus , and the thighs are entirely pale and not black at 
their base in the posterior pair, as in A, sulcatus (fig. 5 # which 
is shaded to show the difference). # 
The larvae, which are (like those of the Carabidce) very vo- 
racious, inhabit the water, living upon other insects and even 
small fishes : the perfect insects, which with their hind legs 
row themselves about with the greatest ease, can also fly well; 
they are exceedingly ravenous, and will destroy each other if 
confined together. 
The plant figured is Myosotis palustris (Marsh Mouse-ear). 
* It is singular that Linnaeus should have been unacquainted with the female 
of our common species, as appears not only from his Works but by his cabinet, 
which Sir James E. Smith politely allowed me to examine a few years since. 
