266 



THE AGRICULTURAL NEWS. 



August 19. 19n. 



INSECT NOTES. 



THE POLLINATION OF THE 

 SMYRNA FIG. 



The Insect Notes in the last two numbers of the Agri- 

 cultural Reivs described remarkable relationships that exist 

 between certain plants and the insects which act as pollen 

 carriers, and thus ensured the development of the ovar_y and 

 the fertility of the seeds. These instances were chiefly of 

 interest on account of their biological features and not 

 because of any economic bearing which they possess. 



The present article, however, gives the principal facts of 

 a relationship between flower and insect which is quite as 

 remarkable as those already described, and it has an added 

 interest in that a very large fruitgrowing industrj', the culti- 

 vation of Smyrna figs, is entirely dependent upon it. 



The following notes on the fertilization of the varieties 

 of Smyrna figs by the minute gall-making insect (Blasfo- 

 pitaga 'jrossoruni) arc taken from the account given in Ze.s 

 Tiisectes, by Henneguy. 



Blastopbaga occurs naturally in the inflorescence of the 

 wild iig or Capri fig, as it is called. From time immemorial 

 the people of the Orient have provided for the fertilization of 

 the cultivated fig by placing in the branches of the latter, at 

 the time of flowering, twigs of the Capri fig bearing rijpening 

 fruits. It was not, however, until within the past few years 

 that the importance of Blastophaga grossoniui as a pollen 

 carrier was recognized. 



The Capri fig produces three generations of fruits per 

 year. The first of these called Mammee, ripening in April, are 

 developed from flowers of the previous autiunn, having remain- 

 ed attached to the tree during the winter. The fruits of the 

 second generation are called rrofichi; these ripen in June. 

 Those in the third generation, ripening in August and Septem- 

 ber, are called Mammoni. At'the time when ihe fruits of one 

 generation are ripening, the flowers of the next are just 

 coming into bloom; for instance, at Naples in April, the 

 Mammee are nearly ripe and the Profichi are in flower at the 

 time that the cultivated figs are in bloom for the first crop 

 of fruits which ripen in June and July. It is at this time 

 that the cultivators lemove the \vild Mamnicc fruits, which are 

 nearly ripe, and distribute them through the branches of the 

 cultivated fig. 



The inflorescence of the wild fig contains a very large 

 number of male or pollen-bearing flowers, while that of the 

 cultivated fig contains almost entirely female flowers. In 

 the former of these there occur immense numberp of a minute 

 Hymenopterous insect — the Blastophaga givs-sornm already 

 mentioned. The insect is developed in the minute gall at 

 the base of the flower where the egg has been inserted into 

 the tissues of the inflorescence by the female parent, with the 

 aid of her piercing ovipositor. 



On the completion of their life-cycle, the female insects, 

 which are winged, leave the inflorescence of the wild fig well 

 covered with the pollen from its male flowers, and proceed to 

 a neighbouring inflorescence. If this latter chances to be 



one of the cultivated figs, its fertilization is provided for by 

 the pollen adhering to the body of the insect. The object of 

 the visit of the insect to these flowers is, of course, the 

 depositing of eggs to provide for the new generation, and she 

 accordingly introduces her eggs into the ovaries of the flowers. 

 AVhen these eggs are deposited in the tissues of the wild fig, 

 they pass through a normal cycle of growth and another 

 generation of insects is produced; but when this egg-laying 

 occurs in the cultivated or Smyrna fig, the insects do not 

 develop, this perhaps being due to the rapid growth of plant 

 tissue which destroys the egg or the very young larva. In 

 addition to the pollination of the cultivated fig, there seems 

 to be a direct effect on the growth of the inflorescence 

 resulting from the irritation caused by the punctures of the 

 ovijiositor of the insect. The combined result of the pollina- 

 tion of the flowers causing the normal seed to develop and of 

 the punctures of the females in egg-laying is to produce 

 a fleshy, sugary fig, which is not to be obtained in any other 

 way. 



This process of introducing the wild figs among the 

 branches of the cultivated figs is known as caprification. 

 Some botanists consider capriflcation as useless, since in some 

 countries, and with man}' species and varieties of figs, excel- 

 lent fruits are produced without this operation. It has been 

 well proved, however, that the Smyrna fig, which is the 

 standard of excellence, can only be produced in its best 

 quality by this process. 



Dr. L. O. Howard, in the Yearhool; of the United States 

 Department of Agriculture for 1900, presents an article 

 entitled Smyrna Fig Culture in the United States. In this 

 he gives an account of the early attempts, in Cali- 

 fornia, to produce figs of the Smyrna varieties, possessing the 

 saiije e.xccUent qualities as those grown in Oriental countries. 

 Dr. Howard shows how the usefulness of capriflcation was 

 discovered, and how the important part played by Blasto- 

 phaga was thoroughly proved. It was not until the fruit 

 growers of California had succeeded in importing Blastophaga 

 and establishing it on Capri fig trees alreadj' growing there, 

 that they were able to produce satisfactory Smyrna figs. 



AGRICULTURAL LECTURES IN ANTIGUA. 



The following list of lectures in connexion with the 

 Courses of Heading of the Department, which are being 

 delivered in Antigua, has been forwarded by Mr. H. A Tem- 

 panj-, B.Sc, Superintendent of Agriculture of the Leeward 

 Islands : — 



Date. Subject. 



July 31 Elementary Botany 



August 7 Some Common Un- 

 soundnesses in Work- 

 ing Stock. 



\i 



28 

 4 



Elementary Botanj- 

 Soils and Manures 



Sept. 



„ 25 In.sects and Fungi 

 October 2 Insecticides and Fun- 

 gicides (at the Botanic 

 Station) 

 ,, 23 Bacteria in relation to 

 Agriculture 



Lecturer. 

 Mr. T. Jackson 

 iMr P. T. Saunders, 

 illt.C.V.S., Veterinary 

 Officer to the Imperial 

 Department of Agricul- 

 ture 



Mr. T. Jack.son 

 Mr. V. M. Weil, B.Sc. 



Mr. H."a. Tempany B.Sc. 



.Mr. T. Jackson 



Mr. H. A. Tempany B.Sc. 



