1922 ENTOMOLOGICAL SOCIETY. 31 



in 1920, from material bred in sequence from eggs laid in May and recovered 

 during July, 55% of the July second-generation puparia hibernated while 45% 

 emerged as third generation adults in mid- August. Second-generation puparia, of 

 course, were being produced during August and September, hence only a fraction 

 of the second generation really produced a third generation. 



From our records we are able to state, therefore, that two generations are 

 complete at Vernon, B.C., while in certain years, a partial third generation 

 occurs. 



Nature op Injuries. 



While adults were extremely active on the wing on bright sunny days and 

 very sluggish on dull, cloudy days, weather conditions did not seem to affect the 

 rate or degree of oviposition per diem. Eggs were laid most frequently on the 

 strongest growing seedlings in the early spring, and at this time of the year 

 oviposition nearly always occurred at or just below the surface of the soil on or 

 in the vicinity of a plant. After the end of June the leaves and leaf sheaths were 

 most favoured, particularly those of the weaker plants or those previously injured 

 by the first generation larvae. Eggs were rarely laid on those plants with the 

 bulb showing and seldom on plants with a prominent meek.' 



In the earlier part of the growing season larvae hatching from eggs laid on 

 the soil surface enter the plant at the junction of the roots and the forming 

 bulb, presumably finding their way down through the soil and not. so far as we 

 have been able to determine, entering the plant in the stem and then passing 

 down to the bulb. The larvae, after feeding at the base o,f the bullb, gradually 

 work their way towards the top, causing the plant to decay and wilt. Partly 

 grown larvae also migrate from one plant to another in a row and have frequently 

 been observed entering the stem of the new plant just below the surface of the 

 soil. These larvae do not necessarily descend to the roots, although this down- 

 ward movement is usual, but occasionally burrow upwards to the tops, causing 

 the leaves to wilt, leaving a sound and uninjured bulb below. 



When eggs are laid on the leaves or in the leaf sheaths the larva? usually 

 find their way to the bulb as soon after hatching as possible by passing down in- 

 side the sheath. Larva? have frequently been taken within the hollow stems 

 from one to six inches above the soil surface, as many as one to sixteen maggots 

 being found at times in a single leaf, but these doubtless have been forced up 

 by the decomposition 'of the bulb and stem below ground rather than have 

 hatched and lived together in the leaves. Larvae, even in small seedling onions, 

 will continue to feed in the plant they are attacking, passing up into the leaf 

 above the soil surface before they migrate to another plant in the same row. 



In general, this insect causes loss by the direct destruction of see'dling 

 onions in the early spring, by the decay or rot of developing bulbs in early summer 

 and by a reduction in weight in the marketable crop as a result of larval feeding 

 which has not been sufficient to cause the death of the plant. 



Control Measures. 



From records under North American conditions it appears to be conceded 

 that soil treatments with gaseous substances, dry and wet applications to the 

 soil surface and such like treatments are of no value under commercial methods 

 of onion growing. Commercial fertilizers have had the effect of increasing the 

 tonnage and have to some extent enabled plants to withstand an attack. The 

 poisoned bait mixture consisting of so'dium arsenite, molasses and water, applied 



