SAXICOLA. 



609 



the insect (according 1 to Reaumur) about ten hours 

 and a half in their construction. The grooves, at 

 first, are scarcely perceivable above the surface of 

 the branch, but, by degrees, become more and more 

 convex by the increased size of the egg, a circum- 

 stance of considerable interest, and quite at variance 

 with the analogy of the eggs of the majority of 

 insects and birds. In some species, however, the 

 eggs are deposited together in a single large groove, 

 and in some species the parts of the leaves wounded 

 by the sawfly produce galls (as in Nematus intcrius, 

 &c.) similar to those formed by the true gallflies. 

 These galls are variable in their form and substance, 

 being either woody or pulpy, and either of the ordi- 

 nary form, or resembling a small fruit. In these 

 species the Iarva3 hatched from the eggs continue to 

 reside within the galls, either alone or in company, 

 but in general the larvae of the sawflies are external 

 feeders, devouring the leaves of trees and plants. 

 These larva 1 , from their general form, and the num- 

 ber of their legs and prolegs, bear a very great resem- 

 blance to the caterpillars of lepidopterous insects, so 

 that they are ordinarily termed by the French natu- 

 ralists fausses chenilles, or false caterpillars. The 

 number of their legs differs from that of the true 

 caterpillars, which have from ten to sixteen ; whereas 

 these false caterpillars have either only six, or from 

 eighteen to twenty-two. Many of these false cater- 

 pillars have the habit, when alarmed, of rolling them- 

 selves up in a spiral manner, like an lulus and 

 others, whilst feeding, generally elevate the hind 

 part of the body in the air, giving themselves a very 

 droll appearance, and twisting their tails about in all 

 directions, In order to undergo their transformations 

 to the pupa state, they construct a cocoon, partly of 

 silk and partly of earth, glued together with a gummy 

 secretion, which they emit from the mouth, and 

 within which they remain for a great length of time 

 without throwing' off their larvse skin. The pupa is 

 incomplete, and closely resembles those of other 

 hymenopterous insects in its general form. Many of 

 these insects are very obnoxious to the agriculturist 

 and horticulturist. Thus the larva of one species 

 preys upon the upper surface of the leaves of barley, 

 and causes it to wither. Another species feeds upon 

 the rose, Athnlia Routs, (Linnaeus) ; and the writer 

 hereof has discovered the preparatory states of 

 a species of Lyda upon the same plant, of the leaves 

 of which the larvse construct a very curious case, in 

 which they reside; and the gooseberry is occa- 

 sionally stripped of its leaves by the larvre of another 

 small species, which is found upon it in very great 

 profusion. This larva is of a greenish colour, 

 covered with minute black tubercles, and at first 

 feeds in society ; but no sooner have they consumed 

 the leaf upon which they were born, than they sepa- 

 rate, and the work of devastation is carried on to 

 such an extent, that in a very short time not a leaf 

 remains on the tree, and the crop of fruit is entirely 

 consumed. Fumigation, by means of sulphur or 

 burnt leaves, may be successfully employed. 



Another species, Tenthredo ccrasi ( Linnaeus), feeds, 

 in the larva state, upon the leaves of the cherry and 

 some other fruit-trees. At this period of its existence 

 it has scarcely the appearance of an insect, being 

 covered with a slimy secretion, which causes it to | 

 resemble the faeces of some small bird (and thus to 

 escape from the insectivorous birds), and which is 

 aided by its sluggish habit, as it does not stir until it 



NAT. HIST. VOL. III. 



has entirely consumed the epidermis of the leaf in its 

 immediate vicinity. In North America the cherry- 

 pear, apple, and plum, are occasionally attacked by 

 another insect very nearly allied to the preceding, 

 and which is there known under the name of the 

 slugworm. In 1797, they entirely covered the 

 smaller trees to such an extent that the atmosphere 

 in the immediate neighbourhood was charged with a 

 sickening odour. Twenty or thirty were to be seen 

 on a single leaf, and, many trees being completely 

 stripped, were obliged to put forth fresh foliage, thus 

 anticipating the supply of the succeeding year, and 

 cutting off the prospect of fruit. (Peck, Nat. Hist, 

 of the Slugworm, quoted by Kirby and Spence). 



But the most destructive insect of the present 

 family is one of which the larva is commonly known 

 under the names of the "blacks" or " niggers," and 

 which have, during several of the past years, entirely 

 consumed many of the turnip crops in the south of 

 England. About twenty years ago they were ob- 

 served to be equally abundant as well as in the year 

 1783. It would therefore form a very interesting 

 and not wholly useless subject of inquiry, to endea- 

 vour to ascertain what identity of natural causes 

 existed in those years in order to permit the develop- 

 ment of the insects to so great an extent. The ad- 

 mirable meteorological tables which are now published 

 from lime to time must evidently be of great service, 

 by taking the averages in prosecuting such an inquiry. 

 These larvae are about half an inch long, and feed 

 upon the fleshy part of the leaf of the turnip, leaving 

 the fibres so clean that the leaves are reduced to 

 perfect skeletons; when disturbed, they roll them- 

 selves up in a spiral manner ; they are of a slaty 

 black colour above, with a pale dirty lateral stripe, 

 which is also the colour of the under surface. It has 

 been observed that they do not attack the Swedes or 

 rape. The most successful remedy which we have 

 yet heard of has been to turn in a great number of 

 ducks among the turnips, accompanied by a boy 

 who brushes the plants with a long stick, which causes 

 the grubs to fall, when they are greedily devoured 

 'by the ducks, which are very fond of these palatable 

 morsels. When full-fed they descend into the earth, 

 form an oval cocoon, and therein undergo their trans- 

 formations. The perfect insect (Athalia centifolice) 

 is about a quarter of an inch long, with the head and 

 antenna? black, the abdomen and legs bright orange, 

 the thorax also orange with dark spots at the base of 

 the wings. In this state indeed it is very conspicu- 

 ous, and an intelligent farmer, by going over his fields, 

 would not only be able to foresee the danger which 

 would ensue to his crops if left untouched, from ob- 

 serving the presence of these flies amongst his plant?, 

 but also probably to some extent be enabled to guard 

 against the danger by employing children to capture 

 and destroy the forerunners of these nigger cater- 

 pillars. 



We shall treat of these insects technically, under 

 the title TENTHREDINID^:. 



SAXICOLA (Chat}. A species of birds belong- 

 ing to Cuvier's dentirostral family of Passeres, and to 

 the small-billed section of the family, and of course 

 insectivorous in their feeding. The characters of the 

 genus are : the bill slender and nearly straight, a little 

 broader than high at the base ; the upper mandible 

 with a ridge which advances on the point, and is 

 covered at the base with some hairs ; the mandibles 

 awl-shaped and pointed, and the upper one curved 



QQ 



