SECTIONAL TRANSACTIONS.— D. 369 



species. In the summer these species occupy the upper layers above 100 m., 

 but after the summer spawning the new generation, as it approaches the 

 older stages, sinks down into layers below 250 m. The gradual descent 

 of the older individuals of the new generation is demonstrated. In colder 

 Antarctic water the spawning is delayed and the growth of the summer 

 generation is retarded so that at mid-winter a population may be found 

 still consisting almost entirely of young stages and the descent from the 

 surface may thus take place later in colder water near the ice edge than 

 in warmer water farther north. Winter is a resting period when little growth 

 occurs , but in the spring the ascent to the surface takes place by the upward 

 migration of late juveniles and adults preparatory to the summer spawning. 



Afternoon. 

 Dr. H. W. Miles. — The fruit-infesting sawflies of Britain (2.15). 



There are eight or nine species of Hoplocampa in Britain and they appear 

 to be associated almost exclusively with the order Rosacese and the genera 

 Pyrus and Primus. The biology of several of the British species has now 

 been studied in some detail. 



Hoplocampa testudinea Kl., infests the fruits of the apple Pyrus malus, 

 and H. flava Lin. infests the fruit of Prunus spinosa and Prunus domestica 

 and its varieties. These two species of sawflies have the flight periods 

 coinciding with the blossoming period of the host plants. They oviposit in 

 the calices and the young larvae tunnel into the developing fruit, each larva 

 often invading several fruits before it attains maturity. Both species are 

 univoltine but there is some evidence that a proportion of the larvae have 

 delayed development and spend almost two complete years in a resting 

 condition in the soil. This phenomenon appears to be associated with 

 the food specialisation of the species and Speyer in Germany has recorded 

 a similar circumstance in Anthonomus pomorum, a fruit-blossom infesting 

 weevil in which a certain proportion of the adults live for two years. 



Certain varieties of apples and plums appear to be more susceptible to 

 attack than others by the sawflies. Within the last two years Hoplocampa 

 brevis Kl., which has been known for some time on the Continent, has been 

 discovered infesting pear fruits in a garden in Cambridge but so far its 

 distribution in Britain is not known. Of the remaining species, H. crataegi 

 Kl. and H. pectoralis Th. are associated with hawthorn fruits, H. ariae 

 Benson with the fruits of Whitebeam, and H. alpina Zet. with the fruits 

 of Mountain Ash. 



Little is known of the biology of H. chrysorrhosa Kl. and H. rutilicornis 

 Kl., but they appear to be associated with Prunus species. 



The particular interest in the sawflies of the genus Hoplocampa occurring 

 in this country is that they all exhibit the fruit-infesting habit in the larval 

 stage and there is a co-ordination of the flight period of the adult insects with 

 the blossoming period of the host plant. 



Mrs. K. Grant. — A historical study of migrations in certain hawkmoths 



(2-45)- 

 Outbreaks of the American and European sub-species of Celerio lineata 

 were studied from journals and from records collected by the Insect Immi- 

 gration Committee of the South-Eastern Union of Scientific Societies. 



It is suggested that both sub-species originate in semi-desert areas, and 

 this idea is supported in the case of the American sub-species by showing 

 that a correlation exists between outbreaks of the moths and a certain 



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