i8 INSECTS. 
most destructive species. The perfect insect appears in May from larvae which 
have passed the winter in their pupae cases, and lays its eggs upon the leaves of 
rape and turnips; as many as two hundred or three hundred eggs being often 
deposited by a single female; and in September and October the ravages of the 
green and black larvae become only too evident. The grub is full grown in October, 
when it descends to the surface of the earth, and forms a cell of earth grains, in 
which it passes the winter. The majority of the members of the family belong to 
the typical genus Tent)'credo, and are elegant, active insects, which alone of all the 
saw-flies exhibit a carnivorous habit. It is not easy to distinguish the males from 
the females, though the difference in the colour is of some assistance. It has been 
noticed, for instance, that in cases where the abdomen of the female is entirely 
black, that of the male is black and red. Of the green saw-fly ( T\ scalaris), the 
larva is common on the willow, and is pale green with black spots on the back, 
sometimes blending to form a central band. The pretty brush-horned rose saw- 
fly (Hylotoma rosai), which in size and colour closely resembles the turnip saw-fly, 
extends throughout Europe, where it is common wherever rose-trees occur; the 
larva being found from July to October on both the wild and cultivated roses. 
When turning to a pupa, it spins an outer meshed envelope, and a more densely 
woven inner one; early larvae pupating at once, and emerging as perfect insects 
early in August. The later broods, however, pass the winter in the pupa case, and 
appear in the following spring. The female makes an incision on the twigs of rose 
bushes, in which she lays her eggs, after which the twig withers away. 
Typical Group— Suborder Petiolata. 
The insects belonging to this second subdivision of the order are distinguish¬ 
able from the last by the petiole, or short stalk joining the abdomen to the thorax. 
Sometimes this stalk is so short that the abdomen and thorax are closely united, 
while in others it is longer, and thus these characters form a fairly natural sub¬ 
division of the Petiolata into the pseudosessile and pedicellate forms. For general 
1, turnip saw-fly and larvte ; 2, rose saw-fly, male; 3, saw-fly, female, and with larvae. (Nat. 
size.) 
