Observations on Insects affecting the Turnip Crops. 55 



hrassic(£ under cabbage-leaves in July, and secreted in the leaves 

 of the crumpled broccoli as late as the end of November, when 

 they v/ere of all ages and sizes, both winged and apterous. 



4. Aphis Floris-rapae, Curtis— the Turnip-flower plant-louse. 



Male — dull pale-green^ dusted with white: antennae mode- 

 rately long, blackish, excepting the base of the third joint: eyes, 

 head, disc of the thorax, and abdomen, varied with black ; tubes 

 short and barrel-shaped: wings similar to those of ^. bras sic ce : 

 legs ochraceous; apex of thighs, shanks, and feet, black (fig. 7). 

 Female — dull pale pea-green, powdered with white : rostrum 

 short and stout : eyes black ; antennse rather short, slightly hairy, 

 terminal -half brownish : abdomen, with the spiracles, and several 

 dots forming two rows towards the apex, black ; tubes short, oval, 

 and black : legs clothed with short hairs ; the feet black (fig. 8). 

 I regret having to draw my description and figure of the male 

 from dead specimens ; for the colours, as well as the form of the 

 body, have changed considerably. 



Towards the end of July I found a multitude of these Aphides "^ 

 secreted amongst the short flower-stalks of the early white Jurnip, j 

 when a few only of the flowers were open. They were of various 

 sizes, but all apterous at that period ; by the middle of August, 

 ^ however, they had increased to very large companies, with a few 

 winged specimens. This species is readily distinguished by its 

 white dusty appearance, with which both sexes are thinly coated, 

 as well as by their short, conical, and black tubes, or ducts : the 

 black spots on the backs of some females were larger, and the 

 horns longer, than in the individual represented in the plate. 



Whether any of the above Aphides deposit the sweet liquor 

 called honey-dew upon the turnip-leaves has not yet been ob- 

 served ; but I have never seen the ants occupied in visiting the 

 infested leaves for the purpose of collecting the saccharine matter 

 which exudes from the two abdominal tubes or ducts, and which 

 is also discharged from the extremity of the bodies of some 

 species."'' 



Protected as the Aphides are in the wrinkles of the leaves, 

 which they themselves have caused by the pumping up and ex- 

 travasation of the sap, it is, I think, impossible in the open field 

 to apply any effectual remedy for the extirpation of this prolific 

 tribe : when it is in our power, the best plan would be to cut off 



yellow, dry, and brittle ; and at an early stage this disease seems to encou- 

 rage the Aphides, owing to the plants not being healthy and able to resist 

 such attacks. 



* The exudation of this honey, which passes off through the tubes, and 

 chrystalises in cold weather, may be a necessary means of disposing of any 

 surplus secretions arising from the constant supply of sap which is passing 

 through the stomachs of these little leeches, and which they may not have 

 the power of discharging fast enough by the usual organs. 



