TUENIP SAWFLY. 
83 
grub is recorded by Mr. Edward Newman as having been found by 
him lying within, and very little altered in the following May. From 
these chrysalids, as mentioned at the beginning of this account, the 
perfect sawflies come out to start the first attack of the summer. 
The mischief caused by the sawfly-caterpillars when they appear, 
as is sometimes the case, in vast hordes, is enormous. They may be 
found swarming on the leaves, and will very rapidly clear away all that 
is not too hard to eat. Severe attacks have been recorded at intervals 
(and once during four successive years) since 1756, but I am not 
aware of a bad widespread outbreak having taken place for several 
years back. 
In 1880 Mr. Eobert Service, writing from Maxwelltown, Dumfries, 
mentioned that he had often met with the insect whilst collecting, and 
had met with it that summer as usual, but that it was rarely injurious 
in that neighbourhood; and in 1882 Mr. George Brown, writing from 
Watten Mains, Caithness, observed that a slight attack had occurred. 
He noted that “the damage sustained was but trifling; still, where 
they were at work can easily be seen, as there is nothing left of the 
leaves but the ribs.”* The only occasion on which I have seen the 
attack myself—and then only as occurring to a slight extent—was 
on a Turnip field at the top of the cliffs above the Severn, at Sedbury 
Park, in W. Gloucestershire. This was in the autumn, and accom¬ 
panied a high wind. From the state of the sawflies on first observa¬ 
tion it appeared as if they had been carried by the gale from fields 
lower down the Bristol Channel, and thrown, partly exhausted, on the 
crop at the first high level, and very slight presence of caterpillar 
followed. 
Very little can be done to prevent this attack, as we very rarely 
know when it is coming, but when it is present all the measures which 
succeed in checking attack of Turnip Fly by shaking the pest from the 
plants, such as sheep-driving, brushing with boughs, &c., and in all 
probability 'dressings obnoxious to the grub, will answer much more 
surely in the case of this attack, for the following reasons : 
The Sawfly-caterpillars eat voraciously, consequently grow fast, and 
therefore have to change their skins frequently, every six days or so. 
When this moult takes place they have to fix themselves firmly by the 
tail-pair of sucker feet to some part of the plant, so as to gain a point 
to pull against in drawing themselves out of the old tight and dead 
skin. If they cannot manage this they die in it. Therefore all 
measures which disturb them in this operation are very practically 
useful to us. 
Also, it appears that up to the time of the first moult the cater¬ 
pillar has the power of spinning a thread, by which it can let itself 
* See Keports of Observations of Injurious Insects respectively for 1880 and 1882. 
