GEOMETERS. 



49 



GEOMETERS 



FAMILY I. URAPTERYD.E 



ANOTHER GREAT DIVISION or TRIBE of 

 Moths are called Geometers (in science, 

 Geometrce), from the peculiar attitude which 

 the caterpillars assume in walking. As a 

 general rule the caterpillars of butterflies 

 and moths, like the insects when they have 

 arrived in the perfect or winged state, have 

 six legs ; but they also have, on the under- 

 side or belly, a number of circular disks 

 fringed all round with delicate hooks, by 

 which they adhere to the twigs or leaves of 

 the plants they feed upon. These adhering 

 disks have been called " prolegs," " abdo- 

 minal legs," or " false legs ;" but the proper 

 name is " claspers," because they clasp the 

 substance on which the caterpillar is feed- 

 iug, and this so tightly, sometimes, that the 

 caterpillar cannot be forced away without 

 injury. The caterpillars of butterflies, as 

 well as those of the Moths I have been 

 describing, have almost invariably ten of 

 these claspers, but the Geometers have only 

 four ; and these are quite at the tail-end, so 

 that the middle part of the body of the 

 caterpillar has no means of taking hold : 

 when, therefore, the caterpillar walks, it 

 first takes hold of the twig with its six 

 proper legs, and holding tightly, lifts up its 

 claspers, and bringing the two ends of its 

 body almost together, again takes hold with 

 the claspers, the back of the creature 

 making an arch or loop ; this position, as 

 I proceedj will be made much more clear 

 by the accurate representations now being 

 prepared, than by any description that I can 

 write. Geometers thus being produced from 

 caterpillars which are smooth and not hairy, 

 and which have but four claspers instead of 

 ten, it is very easy to recognize them in that 



state; but as we usually meet with them 

 in the perfect or winged state, we very 

 naturally wish for characters by which to 

 recognize them in that state also; this, 

 however, is more difficult. Still, I will do 

 my best to explain the principal and general 

 distinctions, requesting my reader to bear 

 constantly in mind that the rules in Natural 

 History, like all other rules, are subject to 

 exceptions. Geometers, then, as a rule, have 

 slender bodies and ample wings ; the thorax 

 is covered with long scales or hairs, but is 

 never crested. All Moths have what may 

 be called a pattern on their wings : now this 

 pattern, in the Nocturni, is generally ex- 

 tremely different in the fore and hind wings. 

 The principal exception to this rule is the 

 family of Emperor Moths ; the Geometers, 

 on the contrary, have not unfrequently the 

 same pattern, or the same distribution of 

 colours, on both pairs of wings. And here 

 I ought to mention that the wing has a 

 bristle on its costal margin, which fits into 

 a sheath on the hind margin of the fore 

 wing ; and a fore wing and a hind wing are 

 thus linked together when the insect flies. 

 The bodies of the Nocturni are often striped 

 or spotted with red or yellow, more rarely 

 with blue ; the bodies of the Geometers are 

 never so adorned. The thorax in Geometers 

 is short and rather square ; the hind legs 

 are furnished with four spines. 



Until the publication of Mr. Doubleday's 

 synonymic list, no attempt had been made 

 to arrange the Geometers of this country 

 in a natural manner. The collector of these 

 beautiful Moths was, therefore, without a 

 guide, and arranged them either by his own 

 fancy, or by their size, or their colour, or, 



M 4 



