284 DR. L. H. GOUGH. 



A question that is frequently asked is, what has been the annual increase of the 

 pink bollworm since the year of its discovery % It has been possible to estimate 

 the annual increase cf Gelechia attack in good tagawi,* as, since the autumn of 1911, 

 the Department (and later the Ministry of Agriculture) has supplied seed for sowing to 

 the fellahin. Samples of this seed, as obtained from the ginneries, have been kept 

 more or less completely since 1912, and a few samples from 1911. This seed is 

 specially selected by the Inspectors of the Ministry of Agriculture, and is somewhat 

 above the average quality. It therefore probably contains less damaged and 

 immature seed than the average. f Seed purchased in any one year is probably 

 of about the same quality in these respects as that bought in any other year ; thus 

 the samples are comparable inter se within given limits. 



In Table II will be found the results of the examination of this seed. In working 

 it up, the gin-broken seed and refuse has been ignored, and only the good seed and 

 the evidently attacked seed counted and weighed. Germination tests have been 

 made only with apparently sound seeds. No " double " seeds were found in the 

 samples saved from the 1911 crop ; some of the seeds had, however, been damaged 

 by insects. Although the absence of " double " seeds suggests the need of caution 

 in ascribing the damage to Gelechia, more especially as the seed was Ashmuni, some 

 of which is known to have been ginned at Maghagha, in Upper Egypt, whence at 

 this time the pest had not been recorded, it appears to be most probable that the pink 

 bollworm had already reached Upper Egypt in that year. The absence of records 

 need not weigh heavily in balancing the evidence, as no system of recording existed 

 at that time, and even single stray contemporary observations, whether positive or 

 negative, are not available now. From 1912 onwards no possible doubt exists, as 

 typical " double " seeds are found in all the samples. 



At the end of Table II all the seed of varieties grown in Lower Egypt has been 

 calculated together in order to facilitate comparison with the figures for Ashmuni, 

 which is the only cotton grown in Upper Egypt. 



Taking the Lower Egypt varieties first, it will be seen that the difference in the 

 extent of the attack, as shown in the Ministry's seed, was much the same in each 

 year for all varieties. It will therefore be more convenient to deal with the combined 

 figures found near the bottom of the table. 



There was a steady increase in the infestation of the cotton seed from 1912 to 

 1915, and a distinct drop in 1917. A little examination of the figures shows that 

 the percentage had in 1916 not reached the expected level, and that improvement 

 had already set in, although the highest point was reached in that year. The rate 

 of increase from 1912 to 1913 was 1 per cent. ; from 1913 to 1914, 2 per cent. ; 

 from 1914 to 1915, 4 per cent. ; in these three years the increase each year had 

 been double that of the year before. In 1916, if this rate of increase had been 

 maintained, 8 per cent, increase could have been expected, whereas only 4 per cent, 

 was found, which in itself amounts to evidence of reduction in the free breeding of 

 the pink bollworm. The figures for the last year of the series are particularly 

 encouraging, as there is an actual fall of 4 per cent, on the figures of the year before. 



* Tagawi = seed intended for sowing, as opposed to tugari = commercial seed. 



f Ashmuni tugari of 1916 averaged 9-7 per cent, against 3-2 per cent, in the tagawi. 

 Sakellarides tugari 1916 averaged 16-3 per cent, against 15'4 per cent, tagawi. Both 

 varieties of tugari were " buono mercantile " or good average commercial seed. 



