78 THE GENERA OF BRITISH MOTHS. 
firmly their six pectoral feet to the substance on which they are standing and then drawing close up to them the 
two posterior pairs of feet, the intermediate segments of the body being raised into a kind of loop, from which 
they are popularly called ‘‘Loopers.” The hind feet are then held firmly fixed while the body is again fully 
extended, when the hind feet are brought close up to them as before, raising the intermediate segments into the 
loop above described. The repetition of this movement gives these singular Caterpillars the appearance of 
carefully measwring the earth, or any other substance, over which they are travelling; and it is upon this idea 
that the name Geometre or Geonvtride which distinguishes this group of insects is founded ; the name being formed 
of two Greek words, meaning ‘‘ the earth” and ‘‘to measure.” Some few of the species have additional pairs 
of ventral legs, but in almost every case they are very minute, indeed altogether rudimental. The great 
muscular power of the larve of some of the Geometridae is very curious, enabling them to rest entirely upon the 
two hind pair of pro-legs, with the rest of the body stiffly extended ; in which position some of the kinds closely 
resemble a dead twig of the branch upon which they are resting. The Chrysalides are rarely subterranean, being 
more often found among dead leaves, sometimes in a loose cocoon, and sometimes suspended by the tail, like those 
of Butterflies. In the perfect state the females often differ in colouring from the males, and in many species they 
are wingless ; in which cases they present a very singular aspect, and the young Naturalist would hardly be 
likely to guess that they were Moths. The colour and markings of this family are in general much brighter 
and more various than in the Noctwide. Most of the Geometridae fly at various hours of the morning and 
evening; and but few of them by night. 
The first Sub-Family of the Geometride is that of the Dasydiadi, containing two genera—Psodos and 
Dasydia. . 
The genus Psodos. In this genus the antenne are simple in both sexes, but the palpi and thorax 
i 
remarkably hairy. The wings are rounded, and in markings approaching those of the Noctuidae, with which this 
genus appears to form a good connecting link, but unfortunately the preparatory stages are but imperfectly 
known : when they are better understood, it may be found necessary to change its present position. There 
is only one British species. 
Psodos Trepidaria (the Black Mountain Moth, No. 1) is a rare species, confined to alpine districts; the © 
only locality where it has been taken plentifully being among the mountains near Rannoch, in the North 
of Perthshire. It is very common in Switzerland, and other mountainous parts of the Continent. 
The genus Dasydia. In this genus the antenne of the male are pectinated in some species and simple 
in others, and slightly thickened. The abdomen is much more slender in the male than the female. The wings 
are dark brown, or nearly black. The preparatory stages are but imperfectly known. Two species of this genus 
are said to be British, but upon the doubtful grounds of a single capture, in the case of D. Torvaria, and but few 
more in D. Obfuscaria. Not having been able to obtain British specimens to draw from, I have not given figures 
of these two species ; the following descriptions will, however, enable Collectors to recognise them if they should f 
be so fortunate as to meet with them. 
Dysidia Torvaria may be distinguished by the dark gray-black of the wings, slightly varied with bands 
of darker, and by the cream-coloured band near the edge on the underside of each wing. The antenne of the 
male are pectinated in this species, A single specimen was taken, many years ago, at Ballymena, in Ireland, 
which Mr. Westwood (Westwood and Humphreys’ ‘ British Moths,” v. ii. p. 67) refers to in the following note : 
“My friend, Mr. Templeton, showed me a black Geometridous Moth, much larger than the Minow Cherophyllata, 
which he had captured on one of the mountains in Ireland, of which at the time I made a sketch, which I have 
unfortunately mislaid,” &e., &e. 
Dasydia Obfuscuria is also deep grayish black, sometimes with a greenish tone, with darker marks. The 
larva is said to be violet gray, with a spiracular white line, an oblique dark gray streak on each segment, and 
haying two small humps on the twelfth segment. Specimens of the perfect insect are said to have been taken at 
Ardrossan, in Arran, and in that famous locality for new species of British Lepidoptera, Rannoch, in Perthshire. 
The second sub-family of Geometride is that of the Fidonidi, containing six genera. 
The genus Speranza. In this genus the antenne are bipectinated in the males. The body is moderately 
