AN INSECT=KILLER.

Dominion, Volume 1, Issue 185, 30 April 1908, Page 4

AN INSECT=KILLER.

LADY-BIRD AND APHIS. TOO PROLIFIC I'"OR THE ENEMY.; (iJY TEI.EGItAI'ir.— SPECIAL COItRESTONDKNT.) • Auckland, April 23. In view of tho introduction of. the lady- . bird into Now Zealand for the purpose of i aphis destruction, the appended extract from the scconcl report of tlio Welcome Rc--7 search Laboratories at the Gordon Menioi rial College, Khartoum, dealing with oxperiI ments made there since the introduction of • lady-birds into the Sudan four years ago, . is of special interest. The report, which t has been received by the local Health Department, is by Dr. Andrew Balfour, medical officer of health, Khartoum. Lady-birds ! wer.o -introduced into the Soudan .with the • idea of checking tho ravages of the aphides, [ but it has been found that no, species of ; lady-bird can increase in numbers to com- . pare with tho aphis. .The.'report; states: — "Tho most as, well as tho most important, in many cases, of the insect enemies is tl™ lady-bird, but no species of . - lady-bird can increase in numbers to compare with an aphis. Few ladv-hirds liavo more than three or four generations a year , in even 'warm climates, while aphides are '.often grandparents before their first month of existence is finished; 'Thus it comes about that' when conditions favour the increaso of tho aphis, and it has even only a short start of a lady-bird'■ enemy, the plant in- ' .fested may bo' severely injured' beforo tho aphis t is' 'suppressed. : A species of aphis sometimes finds our "sweet-pea l plants early in tho spring, and, say, for a week has undisturbed possession. Then the infestation is discovered'by- .'a wandering'lady-bird, and she' at, onco proceeds to avail herself of it, feeding'voraciously herself and laying eggs that her progeny may share the feast-. Tho eggs hatch in about a week,. and then a swarm of hungry larvae slay tlio helpless lice right and left. Doing their best, however, and aided b,y other lady 7 birds which have been attracted to tho scene, they cannot even dispose of the increase. In a few weeks .a second generation ' of' larvae is shortly produced, and , then ' the- aphis is quickly 'overcome.' ' "Sometimes, of course,' the aphis*' is' overcome moro speedily, and sometimes less so. From tho beginning, almost, there was no doubt as to its ultjmatb suppression.' The Jady-bird' larvae wander about when their food supply is exhausted/ but, not having wings,' they do not" 'got very far.,. Somo' eventually find food, and live to propagate, but tho majority die' of starvation, - or 'fall victim -to their cannibalistic brothers,' or to other foes. ' -For weeks at a time there may bo practically no aphis of any kind in tho ■locality, arid then the ' lady-birds becomo -fewer and fewer, so"that/-when aphides, begin to appear agaiii thero are very few lady-, birds about to find th'enu 1 Other: enemies of the aphis kind suffer similarly, These facts render it somewhat doubtful that the injuries to plants from aphides in general could be much lessened by importing new' species of lady-birds, since the newcomers would suffer from the; same disabilities as our native kinds." '■' i The above extract is from notes nia'do'by Mr. Lounshury, Government-'entomologist at Capetown, and Dr: Balfour adds tlio following comrnont on, them:—"Tlicso int-crest-iiig notes present tho somewhat complex' problem which has to ;bo faced when tackling the question of aphis'destruction in a practical manner.' Moreover, it' requires care -arid skill to rear captive' lady-birds, and it' ;is difficult -to fcrd them, j Still, this seems to be tho only likely way iof combating. tho aphis,' and, if successful, both tho agriculturist and the Treasury would greatly bene'fit." ■ >■.' - -