297 



tlie poison is when the leaves are damp and the air cahn. The powei 

 duster recommended should be able to cover at least 6 acres an hour, 

 whereas the capacity of each hand dust-gun is about 5 acres per day. 



Davidson (W. M.). Life History and Habits of the Mealy Plum Aphis. 



—U.S. Dept. Agric, Washington, B.C., Bull. no. 774, 28th April 

 1919, 16 pp., 2 plates. 



Hyahpterus arundinis, F. (mealy plum aphis) in Cahfornia is injurious 

 to plums, prunes and, in a lesser degree, to apricots, causing early 

 dropping and small-sized fruits and probably, to some extent, the 

 apical cracking of prunes. The winter eggs hatch in early March and 

 stem-mothers begin reproduction about 20th March. There are 

 normally from 3 to 5 spring generations, the earlier ones being wingless, 

 while practically all produced after mid-June develop wings, though 

 wingless generations have been known to persist until the autumn. 

 Migration to the summer food-plants, Phragmites sp. (reed grass) and 

 Typlia latifolia (cat-tail rush) continues from April till August [see this 

 Review, Ser. A, v, p. 229, etc.]. About the middle of October winged 

 sexuparous migrants are produced ; these fly to the fruit-trees where 

 sexual females are deposited. Oviposition occurs in November and 

 December. 



Internal parasites of H. arundinis seem to be very rare, but there 

 are many natural enemies. Eggs of Syrphids and Chrysopids were 

 observed as early as 17th March deposited near the stem-mothers on 

 plums. Lamp}Tid beetles appeared locally throughout April, while 

 in May Syrphid larvae, especially those of Lasiophthicus {Catabomba) 

 pyrastri, L., and Coccinellids, chiefly Hippodamia convergens, Guer., 

 were abundant, and a few Hemerobiid larvae were observed. The 

 colonies on Typlia were preyed upon by Syrphid larvae, and those on 

 Phragmites by Coccinellid beetles and by larvae of Leucopis sp. ; in 

 lite autumn the sexual females were attacked by Syrphids and by 

 Triphleps. 



The use of contact insecticides against the growing stem-mothers 

 in early spring and against the sexual females developing on the winter 

 hosts in late autumn should be effective, though they are of little use 

 against the indiviudals of the intermediate generations. 



Whiting (P. AV.). Sex-determination and Biology of a Parasitic Wasp, 



Hadrobracon brevicornis (Wesmael). — Biol. Bidl. Marine Biol. Lab. 

 Woods Hole, Mass. ; Lancaster, Pa., xxxiv, no. 4, April 1918. pp. 

 250-256, 1 fig. [Received 20th May 1919.J 



The individuals of the Braconid, Hadrobracon brevicornis, mate 

 readily as soon as they emerge from the cocoon, and the females 

 oviposit upon the bodies of mature caterpillars of Ephestia kiihniella, 

 Z., (Mediterranean flour-moth), and probably also upon other cater- 

 pillars infesting flour, etc. Several eggs are laid upon one caterpillar 

 and as many as 10 or 12 parasites may sometimes develop from it, 

 though the number is usually smaller. At a high temperature the 

 length of a generation is 10 days or less. The adult females may live 

 as long as 6 weeks. 



Sex-determination experiments showed that in H. brevicornis 

 fertilised eggs produce females and unfertilised eggs produce males, 



(C571) o 



