THE SWALLOW-TAILED MOTH. 447 



very carefully applied, as those readers well know who have 

 practically studied gymnastics. The leverage is so great that 

 the strongest and most accomplished gymnast cannot maintain 

 his position for any length of time, the attitude requiring the 

 strongest possible strain on the muscles. Yet this attitude is 

 not only easy to the Geometrse, but appears in some cases to 

 be the chosen attitude of rest. 



Several of these larvae pass a large portion of their time 

 stretched out at full length from the twig on which they are 

 clinging. In this attitude they so exactly resemble twigs, that 

 the sharpest eye can scarcely detect them, and even the most 

 experienced entomologists are often deceived, taking veritable 

 twigs for caterpillars, and caterpillars for twigs. None of the 

 caterpillars are hairy, and their smooth bodies, often furnished 

 with blunt spikes or humps, bear the most curious resemblance 

 to the smooth-barked, bud-bearing twigs of the trees on which 

 thej live. Such caterpillars can be at once recognised as 

 belonging to the Greometrae, and every entomologist knows that 

 if he should find a looping caterpillar, and rear it, the result 

 will certainly be a Greometra Moth of some kind. 



In the perfect state it is not so easy to distinguish the 

 Greometrsp, though there is a certain and almost indescribable 

 aspect about them that a practised entomologist rarely fails to 

 detect, even though the species be new to him. We will now 

 proceed to examine some of the most characteristic of these ' 

 Moths in detail. 



The first family of the Geometrse is called Urapteryd^, or 

 Wing-tail Moths, because in them the hinder wings are drawn 

 out into long projections, popularly called ' tails.' In England 

 we have but one insect belonging to this family, the beautiful, 

 though pale-coloured, Swallow-tailed Moth {Urapteryx sam- 

 bucata). The generic name is spelt in various ways, some 

 writers wishing exactly to represent the Greek letters of which 

 it is composed, and others following the conventional form 

 which is generally in use. If the precisians are to be followed, 

 the word ought to be spelled Ourapteryx. 



There is no difficulty in recognising this Moth, the colour 

 and shape being so decided. Both pairs of wings are delicate 

 yellow, and the upper pair are crossed by two narrow browD 



