Appendix: Entomology of the Rose. 365 



has also been observed that they increase in size after they are laid, and although this 

 growth of the egg is contrary to the analogy observable in the eggs of birds, and even of 

 most insects, it has its advantages, for as it continues to increase it raises the bark more 

 and more, and consequently widens at the same time the slit at the entrance, so that, with 

 species which feed on the leaves of the plant, the grub when 'hatched finds a passage 

 ready for its exit.* The young caterpillar of Tenthredo cincta, when hatched, works 

 its way at once into the pith of the young shoot, and by feeding upon it causes the 

 shoot ultimately to perish. It commences at the top and works downwards, and its pro- 

 gress may be traced by the drooping condition of the leaves, which gradually flag as the 

 nourishment necessary to their existence is absorbed, and occasionally more than one larva is to 

 be found in the same shoot. By the time it is full fed the larva has generally reached the hard 

 wood of the plant, and making for itself a chamber in the pith there changes to the pupa state. 

 The larva is dark green, with a pale line along each side ; the fly is about one-third of an inch in 

 length (larger than the last described) and of slender form ; the expanse of the wings when 

 stretched out is rather nore than half an inch from tip to tip ; head, antennje, and body are 

 shining black, the last with a transverse whitish band towards the tail ; the legs have the first 

 joint black, the rest yellow. The perfect fly is to be found in the spring, the caterpillar in the 

 summer. It passes the winter in the pupa state. The best way of destroying the insect is to cut 

 off and burn the infected shoots. 



One of the commonest species of saw-flies in most districts is that known as Tenthredo 

 rosarum. The economy of this species with regard to the laying of its eggs is equally curious 

 and interesting with that of the last species. Again Rennie's description of the process is so 

 full and exact that no apology to the reader will be necessary for reproducing it. He says : 

 " When the female saw fly has selected the branch of a Hose tree in which to deposit her eggs, 

 she may be seen bending the end of her belly inwards, in form of a crescent, and protruding her 

 saw at the same time to penetrate the bark or wood. She maintains this recurved position so 

 long as she works in deepening the groove she is making ; but when she has attained the depth 

 required she unbends her body into a straight line, and in this position works upon the place ' 

 lengthwise by applying the saw more horizontally. When she has rendered the groove as large 

 as she wishes the motion of the tendons ceases and an egg is placed in the cavity. The saw is 

 then withdrawn with the sheath for about two-thirds of its length, and at the same moment a 

 sort of frothy liquid, similar to a lather made with soap, is dropped over the egg, either for the 

 purpose of gluing it in its place or sheathing it from the action of the juices of the tree. She 

 proceeds in the same manner in sawing out a second groove, and so on in succession till she has 

 deposited all her eggs, sometimes to the number of twenty -four. The grooves are usually 

 placed in a line at a small distance from one another on the same branch, but sometimes the 

 mother fly shifts to another or to a different part of the branch when she is either scared or 

 finds it unsuitable. She commonly also takes more than one day to the work, notwithstand- 

 ing the superiority of her tools. Reaumur has seen a saw fly make six grooves in succession, 

 which occiipied her about ten hours and a half. The grooves when finished had externally 

 little elevation above the level of the bark, appearing like a puncture of a lancet in the human 

 skin." As in the case of the species last described, the egg grows after being laid, and the 

 mother fly seems to be aware of this, for she takes care to deposit them at such distances as 

 may prevent their disturbing one another by their development. The young caterpillars when 

 hatched feed upon the leaves of the Rose ; they are dark yellow in colour, having the sides of a 

 pale yellowish green and the belly whitish. This is a double-brooded species, the larva 



* This account is compiled from Rennie's valuable and entertaining work on "Insect Architecture," than 

 which no work perhaps furnishes more interesting matter to the entomologist. 



