118 



foliage with Paris green, lead arsenate, lead chromate and nicotine. 

 These insecticides are arranged in the following order of efficiency :— 

 (1) Nicotine, 10 per cent, of buds remaining infested as against 85 per 

 cent, in unsprayed control trees, while the trees were marked by 

 superiority of growth, the absence of ragged and distorted leaves and 

 freedom from Aphids and spiders ; (2) lead arsenate, which ai^ected 

 the appearance of the trees for several months, leaving them with a 

 thin, milky-white coating not easily washed off by rain, w^hile 55 per 

 cent, of the buds became infested ; (3) lead chromate, which made 

 yellow patches on the leaves, while 75 per cent, of the buds became 

 infested ; (4) Paris green, which had no effect either on the foliage or 

 the pest. 



Fumigation of the eggs on a young plant in a chamber with hydro- 

 cyanic acid gas at the rate of 1 oz. cyanide to 300 cu. ft. of space had 

 no effect whatever, while another attempt with stronger gas in a space 

 of 12| cu. ft. killed only 5 out of 14 eggs experimented upon. 



Morris (H. M.). On the Larval and Pupal Stages of Bibio johannis L. 

 — Ann. App. Biol., London, iv, no. 3, December 1917, pp. 91-109, 

 1 plate, 12 figs. 



Bibio johannis, L., reared from larvae found in the soil of a 

 permanent pasture in Cheshire, is fully dealt with on account of the 

 frequent occurrence of larvae of this family, their possible economic 

 importance, and the absence of any complete account of any Bibionid 

 larva. 



Under laboratory conditions the egg hatches in 48 days, and the 

 larva enters the second stage 19 days later. In the field the larvae 

 are usually found not more than half an inch below the surface, among 

 the roots of the pasture grasses, while others are actually on the 

 surface of the soil usually in small colonies. They feed on decaying 

 vegetable matter only, in which the soil of the pasture under 

 consideration was particularly rich, particles of soil and humus being 

 worked into the alimentary canal by slow movement of the mandibles. 

 The larvae have also been recorded from cow-dung, horse-dung, and 

 other situations rich in decapng vegetable matter, such as garden 

 soil and the base of decaying tree stumps, while larvae of this genus 

 can apparently feed on the roots of living plants. No parasites have 

 been met with in connection with this larva, there being only one 

 doubtful record of a Hymenopterous parasite. The larvae are 

 practically imaffected by cold, no deep descent into the soil being made, 

 even in the severest winter. Under laboratory conditions the pujDal 

 stage lasted for about 15 days, the second larval stage, in which the 

 insect hibernates, having extended from mid-June till the end of the 

 following March. The adults, on emergence, showed a considerable 

 preponderance of males. 



As regards the economic importance of the family, Dilophus febrilis 

 and D. vulgaris have been recorded as causing damage to the roots of 

 oats, grass, lettuce, seedhng cabbage, young flower plants and 

 especially hops ; Bibio marci feeding on potatoes and damaging 

 tomatoes, young conifers, seedhng ash and young spruce ; B. johannis 

 damaging larch seedlings and hop roots, probably introduced in 



