Pri)CEi:i)Ini;s, IDir,. S.") 



iiifcsfccl tiirnip. iinishinl. or ra|ic Icavi's. They hatch in llic spriii;; iiiti) wiii^'loss 

 fciiiaU' niihidrs. known ns •■ strni niothcrs." These iiiatnro in alioni iwo weeks and 

 licfiin ;;ivin;,' liirth lo another iri'neration of females, whieh in llieii- turn mature 

 raiiiilly anil are soon ariively producing a third generation. This rapid ]iroduc- 

 lion of new L'l'neral ions of wingless females continues throughout the suunner. 

 (i.-e.-isionally w ini-'rd speriniens ajipear. and fly to new plant.s. thus S[)readiug the 

 infestalion. .Males are nol jiroilnnMl inilil tin' f.all. These mate with the females, 

 and as a result tin' latter prodme ol'-'s insle.id of living yming. It is these eggs 

 whii-h pass the winter: no oilier sI.il-c of I. hnissii-ir is alile to do so. 



i.f \lillis I,:- 



as l;nil 





The alarniing rate at which tin'se apliidos inrroas<' iiiiglil niali le woiulor le.w 



it is llial all eahliages. wherever this \n'st is foniid. are not invariably and ijiiirkly 

 destroyed. One. and perhaps the ehi(!f. reason is that the aphis li.as several natural 

 (•iieiiiies wliieh are continuall.v reducing I heir nuinlcrs. 



These enendes are diviileil into two classes — viz.. predators and ii.irasiles. 

 .\niong the jiredalors are found liotli the l.-irv.-e aial adults of ladyldids {Cmiiiirl- 

 li(lir\. the larv.-e of hover-flies t l^iiriiliiihr) . and Ihe l.-irv.-e of lace-wings [('Itnjsiiiiiilti ] . 

 These we can prohahl.v aid or harm Init Utile. Se\er.il parasites have heen hreil 

 from Aphis hraxxicir in different ]iarts of the coin ineiil. Inil fnnn material studied 

 in South Alhert.-i dnrin-' T.114 and 1'.n."i one s]ieeies oidy h.-is hi'en IhmmI. This is a 

 small Hymenopteron. n.-inied Din ii Inn nijid ('nrl. Since this spei-ies |iar;isiti7,es a 

 lar.ge percentage of the apliides. and it is present in th<' tields and gardens from 

 Ihe time when the stem nioihcrs h.ilcli. il is ver.v \aliialile for iireveid in;; oiitl reaks 

 of cahha.ge-aphis. 



The life-history of this par.-isiie is similar to that of most of tin' ,i|iins parasites. 

 The adult huries its e-g inside an apliis with lie' aid of its oviposilor. From lliis 

 egg Initches an (jrange-coloure(l \.\v\:[. whicli develops r.apidly at Ihe e.\]iensi> of ils 

 host. \\y the time it is fnll-grown the hody of the aiiliis li.is hecome innch swollen. 

 and is almost sphefical. while its "skin" has clianged from a dull-grey lo a straw- 

 yellow eolonr. and is of a parehment-Iike consistency. The |iarasitie larva liy this 

 time completely Alls the dead aiihis. which is flrmly cemenled to the eahli.-ige-leaf 

 upon which it was feedin.ir. Within it the parasite pujiates, and Liter llie .■idult 

 emerges through a circular hole. How many generations of this jiarasiie there are 

 in a year we do not know, hut llicre must l,e several. The most import.-iiit point for 

 lis to consider is the manner in which the winter is jiassed. 



I.ale in the fall man.v of tlie ii|ihides contain fully develo|ied parasilic larva', 

 piiliie. or occasiouall.y adults which have not emer,i;ed. These aphides, with Iheir 

 contained parasites, are so firmly attached to Hie calihage leaves and slumps that 

 they rein.iin on them throughout Ihe winler. The lirsl .severe frosis kill off .all 



normal apliid<'S. leaving only Ihe jiarasilizcil spi.cimens 1 llie small Mack eggs 



produced hy the fertilized female aphides of tlie lasl uemrai ion. 



If we examine some of the parasitized aphides in llic early spring wi' liiid that 

 in most cases where they contain a full-grown llinii tiix lar\a this larva is ali\e .'iiid 

 licallhy. We liiid also lli.il tlii' pupa' of Ihe species lia\e [i.assed Hie winter siK'cess- 

 rmiy. iail that llie few adnlls which we dissect oiil an> in evei-y case dead. 



During the lirsl week in .\pril adnlls le-an to lialcli fn>m mali-rial colli'cleil at 

 I.ethhridge earlim- in Ihe sprim:. From this it is seen that foih the aphis and ils 

 v.llualle parasite ii.ass Ihe winler on the e.ill a^'e sluiiiiis and le.ives. 



In ]iassiiig. \\c migli! mention that in soin,' of Ihe p.arasilized aphides we found 

 an unwelcome guest, wliich w.is passing the winter in the same stages of develop- 



