252 NATURAL HISTORY. [cH. XVII. 



to the branches ; and unless we were well convin- 

 ced that they had descended to the earth, their sud- 

 den disappearance might just as rationally be at- 

 tributed to their being- borne away by the wind, as 

 that their equally sudden appearance is owing to 

 their being brought as blight by the east wind. 



Having completed their cells or cocoons, they re- 

 main enclosed in a state of inactivity, and under the 

 form of larvae, for a considerable time, without 

 changing to nymphs ; indeed, as there is but one 

 generation of them in the course of a year, and they 

 only remain about a month in the active larva state, 

 it must follow that this state of inactivity must last 

 more than three quarters of a year, after which they 

 become inactive pupa;, under which form they only 

 remain for about a fortnight or three weeks ; in this 

 state their future limbs are all plainly visible, the 

 wings, legs, and antennae being folded along the 

 breast. 



From the great similarity in form which exists 

 between the larvae of the sawflies and the caterpil- 

 lars of the lepidoptera, it is not surprising that the 

 insidious ichneumon-flies attack the former as well 

 as the latter, which are their more ordinary prey. 

 Several instances of this have come under our own 

 knowledge, and in the Magazine of Natural History 

 will be found an account of their ravages upon one 

 of the larger British species of Tenthredinidae. 



It is very seldom that the larvae which we have 

 endeavoured to rear have arrived at the perfect state 

 when kept in breeding-boxes, owing to the difficulty 

 of preserving the earth at a proper degree of moist- 

 ure ; indeed, Geoffroy states, that notwithstanding 

 all the care which he took in rearing upwards of 

 three hundred larvae, not more than four or five spe- 

 cimens arrived at the state of the winged insect. 



Many species, when arrived at the latter state, feed 

 only upon the nectar of flowers ; but there are some 

 species, such as the water and green sandflies {Ten- 

 thredo strophularKZ and vindis), which prey with 



