TURNIP SAWFLY. 



195 



field of Turnips, excepting such of the veins as are too hard 

 to be eaten, in the course of a few days. 



Athalia spinarum : caterpillars, pui^a, and pupa-case, 

 with lines showing nat. size. 



Sawfly, magnified, 



Taking the dates of some attacks which are especially 

 recorded, we find them noticed in 1756, 1760, 1782, 1806, 

 1818, 1833, 1835, and the following years up to 1838; in 1782 

 it was estimated that about two-thirds of the Turnip-ground 

 in Norfolk had consequently to be ploughed and re-sown ; but 

 the worst attack recorded took place in the dry summer of 

 1835, when the injury to the Turnips extended as far north 

 as Durham ; and in the southern counties, from Somerset to 

 Kent, the crop was a failure, the second and even the third 

 sowing being devoured by these " Niggers." 



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 

 observation 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. The worst instance of 

 infestation (reported to myself) was in 1881 on some Turnips 

 near Ashford, Kent. After coming into rough leaf, the black 

 caterpillars attacked them and cleared them in a few days. 

 The loss was estimated at about £,7 per acre. 



The Turnip Sawflies which produce these caterpillars are 

 dull and torpid in moist and cloudy weather, but they thrive 

 and fly actively in warmth and sunshine ; and it is during 

 the period when the sunshine is hottest that pairing takes 

 place. 



The eggs are laid one by one in small slits cut for them in 

 the margin of the leaf by the saw-like ovipositor of the female 



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