380 



Obsef-vations 07i the Turnip Saw-Fly. 



single bird^ by tbe prodigious number it vv^ould destroy in a few 

 days, is scarcely to be calculated. 



It is remarkable that so few parasitic insects seem to be attached 

 to this insect, which may be one cause of its rapid increase ; 

 but I believe that the currant saw-fly is equally free from such 

 enemies. I have bred a considerable number of both species, yet 

 I never detected a caterpillar that had been stung, or in any way 

 inoculated, by parasites ; I am therefore led to conclude that it is 

 of rare occurrence. A friend, however, sent me an ichneumon 

 which appeared to be bred from a cocoon the beginning of May ; 

 it is, I believe, a Bassus of Gravenhorst,* and is black, minutely 

 punctured and finely pubescent; the horns are as long as the 

 body ; the mouth and lower part of the face are white, with a 

 black stripe down the middle, and two points on each side of the 

 clypeus of the same colour, the labrum and tips of the mandibles 

 are ferruginous brown ; the wings are iridescent, the costa and 

 stigma fulvous, the nervures brown, and there is no areolet ; the 

 legs are rather stout and rufous, the cox^ ochreous, the tarsi and 

 hinder tibiae are tawny, the latter with the terminal half and the tarsi 

 black. It is 2| lines long, and the wings expand nearly 5^ lines, 

 not quite | an inch. As it does not appear to be described by any 

 author, I propose calling it Bassus athaliaperda, the " Athalia- 

 destroyer." Mr. Yarreli has also figured " a dipterous parasite (one 

 of the Muscidse), which, having completely devoured the interior 

 of the larva, has undergone its change to a coarctate pupa within 

 the skin of the larva of the athalia, portions of which (greatly 

 stretched) are seen remaining on the outside of the dipterous 

 pupa, as well as the head of the larva, which remains entire."| 

 From our present knowledge, therefore, we have no just grounds 

 to expect assistance from insectivorous parasites, which are often 

 so admirably employed to keep in check the insects that are 

 injurious to man; it is consequently to his own resources that the 

 agriculturist must look for either a preventive or cure ; and with 

 this view we will now proceed to the remedies proposed : many 

 of them, however, are mere palliatives, being limited, imperfect, 

 and uncertain in their operations, whilst others have been at- 

 tended with universal and complete success. 



Mr. Saunders says that " lime- dust or powdered chalk had 

 been spread over the attacked half of a field, and apparently with 

 beneficial results, but few caterpillars remaining;" in another 

 instance strewing quick-lime, and renewing it as often as the wet 

 or wind rendered it necessary, was most beneficial ; but other 

 parties found sowing with lime in the middle of the night, when 



* Curtis's Guide to an Arrangement of British Insects, Genus 520. 



t Trans. Zool. Soc, vol. li. pi. 14, f. 12. su- 



