613 



about the middle of September, when the numbers on apple began 

 to rise, and continued to do so into October ; at this time the infesta- 

 tion on wild trees was insignificant. Figures are not available for 

 the period prior to 1st August, but it is known that there is an outward 

 migration from the orchard to wild trees and a later return migration. 

 It is not yet known to what extent natural control or other causes 

 affect the rise and fall of the insect in orchards. 



Investigations into the rate of reinfestation show that where the 

 pest has been controlled during the early part of the season, sufficient 

 numbers of new individuals from neighbouring, untreated orchards 

 may occur during the summer and autumn to reinfest the orchard 

 for the following year. It appears to be difficult to employ methods that 

 will destroy the adults over a large area late in August before oviposition. 

 ''^^ Notes are given on the mating and egg-laying habits of this 

 Psyllid. Eggs are laid preferably on the smaller twigs of older trees 

 of bearing age. 



CusciANNA (N.). Osservazioni suU' attrazione esercitata dagli odori 

 sugli insetti. [Observations on the Attraction exercised on 

 Insects by Odours.] — Boll. Lab. Zool. gen. S- agrar. R. Sciiola sup. 

 Agric, Portici, xv, 25th June 1922, pp. 226-253. [Received 

 14th October 1922.] 



The author's experiments were made in 1920-21, the odours 

 used being grouped as aromatic, ethereal, balsamic, and nauseous. 

 Detailed results are given. 



The attraction of odours is almost exclusively confined to Diptera. 

 Among the Diptera the families chiefly affected were Anthomyiids, 

 Tachinids and Ortalids, represented respectively by 29-01, 25-50 

 and 41-60 per cent, of the total catches, the Drosophilids being the 

 principal family in the remainder. Among the Ortalids the genus 

 Platystoma occupies the first place. It is not sensitive to balsamic 

 or ethereal odours, but all others indifferently are attractive. Some 

 hundreds of Euxesta nitidiventris, an American species probably 

 •imported into Italy with dried fruit, were taken with vinegar only. 

 Among the Anthomyiids the genera Anthomyia and Hylemyia are 

 responsive to odours of all the groups tested ; the genus Muscina is 

 taken in large numbers with vinegar or nauseous-smelling substances. 

 Among the Tachinids the genus Liicilia is captured in abundance 

 with nauseous odours, while Calliphora and Sarcophaga behave 

 uniformly towards odours. 



Among insects of other Orders, Noctuids among Lepidoptera and 

 wasps among Hymenoptera are responsive to odours, the respective 

 proportions being 1-35 and 0-60 per cent, of the total number of 

 insects caught. 



Vinegar and fruit ferments attracted the majority of Platystoma, 

 carrion and garbage flies, Noctuids and waspS; Vinegar attracts all 

 Diptera sensitive to odours. Ethereal and balsamic odours are inferior 

 to vinegar and nauseous odours. Aromatic and other odours tried 

 were found to have a very feeble effect, or none at all. Vinegar 

 becomes less attractive when diluted. Flower and fruit essences 

 become more attractive. The largest number of Diptera were captured 

 with strengths of 1 : 100, 1 : 500 and 1 : 1,000, the optimum for balsamic 

 odours being 1 : 100, and 1 : 500-1 : 1,000 for ethereal odours. The 

 surrounding conditions are of importance. Calm, windless days 

 with a temperature between 22° and 30° C. [71-6° and 86° F.] provide 

 the best conditions. 



