386 



Observations on the Turnip Saw-Fly. 



tliej made their appearance to apply a remedy? And tliis proves 

 how essential it is to be able to recognise the saiv-fly, in order to 

 be on our guard, and prepare at once for the worst. With this 

 object in view, I have endeavoured to render the engraving as in- 

 telligible and complete as possible ; and as a summary of the 

 foregoing details will be useful for reference;, I shall proceed to 

 lay it before the reader. 



It has been shown in a former report that the turnip-fly 

 (Altica Nemorum) is only to be dreaded in its perfect or beetle 

 state ; but it is quite otherwise with the turnip saw-fly, the cater- 

 pillar or larva of which is the only state in which it is capable of 

 doing any mischief. 



The turnip saw-fly is called by scientific men Athalia sj^i- 

 oiarum, and also Tenthredo centifolicc. These flies come over 

 from the north of Europe, but are probably bred in small num- 

 bers annually in England. 



It is eighty-Jive years since their first appearance was re- 

 corded. 



Their mischievous visits are at extremely irregular intervals. 



In 1782 many thousands of acres were entirely destroyed in the 

 county of Norfolk by the black caterpillar. 



Subsequently to 1782, the year 1835 has proved the most fatal 

 to the turnip- crops from their attacks, the produce of a second 

 and third sowing being destroyed by the black caterpillars. 



In July, August, and September, the saw-flies are most abun- 

 dant ; but they have been found as early as the 29th of March, and 

 as late as the middle of October. 



The male saiv-flies are the smallest, and hatch first : they are 

 supposed to be most abundant, but my experience leads to an 

 opposite conclusion. 



On being touched they feign death ; and are torpid in moist 

 and cloudy weather, but very active in the sunshine. 



They rest by night on plants and flowers, and feed upon the 

 pollen. 



They seem to fly against the wind, like the turnip-beetles. 



JV atering the plants as soon as the saw-flies appear would in 

 all probability preserve the crop. 



Scattering finely-powdered salt over the turnips when they are 

 wet would keep the females from depositing their eggs. ' 



The eggs are laid immediately after pairing, between the cuti- 

 cles of the leaf, close to the margin, or in the edge of a large hole, 

 and are deposited singly in cells. 



Outside rough leaves are selected for this purpose; and the 

 leaflets at the base are often preferred. 



The turnip saw-flies live twelve or fourteen days, and the 

 females are exceedingly tenacious of life. 



