May 1, 1893.] 



KNOWLEDGE 



87 



was previously the last turn into an internal position 

 where it may be eaten with impunity. In this sort of 

 life some two or three weeks are spent. If the insect 

 is disturbed in any way, as by jarring the branch, or 

 meddlinp; with the leaf, it usually prefers not to rely on 

 the concealment afibrdcd by its retreat, but to rush out 

 into the open. Wriggling through the outer end of the 

 tunnel, it drops towards the ground, at the same time 

 running out a thread, at the end of which it hangs sus- 

 pended in mid-air some six or seven feet down. By this 

 thread it can regain its cell when the danger is past. No 

 doubt they often escape from birds in this way, as the 

 thread is almost invisible, and therefore the insect, by 

 suddenly dropping out of the tube at the opposite end to 

 that where the enemy is posted, passes instantaneously 

 out of the range of its hunter's vision and saves its 

 life. 



In due time it changes to a reddish-brown chrysalis 

 inside its leafy coil. This, too, is very active, wriggling 

 violently if at all disturbed. The segments of the abdomen 

 of the chrysalis are each furnished with two rows of little 

 hooks (Fig. 8), which are of great importance to 

 the insect when it is ready to become a moth. When 

 the critical moment has arrived the 

 chrysalis works itself along by the help of 

 the hooks to the open end of the tunnel, 

 and thrusts the fi'ont half of its body 

 through the apertare. Then the skin splits 

 as usual in the exposed part, and the httle 

 moth drags itself out of its case, and 

 prepares to spend the few remaining 

 days of its hfe in the open air, sitting 

 about on leaves, or fluttering round the 

 bushes in an intermittent and sluggish 

 way. 



The green oak moth is sometimes so 

 numerous as to be exceedingly destructive, 

 quite stripping the trees of their first crop 

 of leaves, but at the same time providing 

 a glorious feast for the insectivorous birds 

 which chatter around in exultant chorus, 

 expressive no doubt of supreme delight. Such was the 

 case last year, when, in a certain wood near London, 

 at the end of May, every oak tree over a particular 

 area was black and bare at a time when all the trees 

 of other kinds around were brilliant with the fresh green 

 spring foliage. If the trees were shaken, down fell 

 showers of caterpillars, some precipitated to the earth by 

 the violence of the jerk, others hanging from threads and 

 dangling about in mid-air. A little later in the season, 

 similar shaking would bring down a shower of chrysalids. 

 The leaves of these trees were so completely destroyed that, 

 had it not been for their dried and withered fragments still 

 held together by the little silken cords, one would have 

 imagined that no leaves had yet been produced. For- 

 tunately, they were replaced by a second crop after their 

 destroyers had passed beyond the stage of leaf eating. 

 Many others of the Tortrices carry out their designs in 

 essentially the same way, only varying the details. Some, I 

 for example, simply double the two halves of a leaf upon 

 one another ; others fasten several leaves together and ] 

 take up their abode in the midst ; others, again, make an 

 incision into a leaf and then turn down or roll up the flap 

 so loosened. In gardens, rose trees are very liable to the 

 attacks of several species, some of which, exceedingly hand- 

 some little orange-coloured moths, fold up the leaves, 

 while others establish themselves within the young flower 

 buds and devour them. 



{To be continued.) 



THE NUTHATCH. 



By HaKRY F'. WlTHEIiHY. 



Fio. 8. — Body 

 of clirysalis of 



i Leaf Boiler, 

 showiuo; hooks. 



THE nuthatch (Sitta chco/jo-'?) is the only repre- 

 sentative of the genus Sittn to be found in Great 

 Britain. 

 It is tolerably abundant in England, especially 

 in wooded districts, and it remains with us all the 

 year round. It is not found either in Scotland or Ireland. 

 The nuthatch belongs to the same order, or family, of 

 birds as the woodpecker genus, i.i'., the scansores, or 

 climbers, and it is a very good type of that order. 



The general colom-ing of the bird is bluish-grey on the 

 back and upper side of the wings, and buff on the breast, 

 shading to a bright chestnut on the under tail-coverts. 

 The upper and under side of the bird thus produce a 

 beautiful contrast in colour. The throat is silvery white. 

 A black line of feathers, very similar to the " moustache " 

 of the woodpecker, runs from the base of the mandible 

 through the eye to the bird's shoulder. 



In comparing the nuthatch with the genus Pinis, or 

 woodpeckers, a great difference in the respective form of 

 each is noticeable, and especially in the shape and texture 

 of the tail feathers. We have already seen that the wood- 

 pecker's tail feathers are long and pointed, and that being 

 strong they are very useful to the bird when climbing, 

 whilst the tail of the nuthatch, on the other hand, is 

 short and square, and is composed of soft feathers, which 

 could not be so used. The nuthatch is extremely agile in 

 its movements, and a long tail would no doubt be an 

 inconvenience to it, whereas its short tail never impedes it. 

 The lack of usefulness in the tail for climbing purposes 

 is amply made up by the construction of the bird's foot. 

 This has three toes pointing to the front and one behind, 

 all of which are armed with strong, sharp claws, curved 

 at the ends. The hind toe and claw are much longer 

 and stouter than the others. 



The bird is seldom seen upon the ground, but lives 

 in the trees. With the help of the claws it is enabled to 

 climb with the most extraordinary ease. The bird is 

 remarkable for its agility, and is scarcely ever seen at rest, 

 nor does it seem to be impeded by the law of gravity in 

 the slightest degree ■v\hen climbing, for it will descend the 

 tree head foremost, a feat which no other bird of its tribe 

 can perfoim. It creeps along the under side of a branch 

 as frequently as on the upper side. The nuthatch dees not 

 climb with a jerky motion like our woodpeckers, but creeps, 

 or rather runs, along as Emoothly as a mouse. 



The food of this bird is chiefly composed of insects, 

 berries, acorns, and beech-mast, but it is also very fond e f 

 the kernels of hazel nuts, which it extracts from the shell 

 in a very clever way. Having obtained a nut from a tree, 

 or from some store hidden by the bird itself, it carries the 

 treasure in the beak to some rough-barked tree hard by, 

 such as an old oak or old biich, and then proceeds to fix 

 ihe nut securely in a crevice of the baik. The bird then 

 commences to hammer with its beak until it has made a 

 hole in the shell large enough to extract the kernel. 

 Occasionally the bird will place itself over the nut, and 

 attack it head down, probably to give additional force to 

 its blows. Should the nut be dislodged during the 

 operation, the bird is co marvellously quick that it will 

 invariably catch it in its beak before it reaches the ground. 

 From this habit of brealdug nuts, it has earned the name 

 of nuthatch, which is probably derived fi-om the French 

 " hacher" to chop, hence our hatchet. 



While clinging to the bark to deliver a blow, the bird is 

 greatly supported on the hind part of the leg, which may. 



