490 



is only about one-half or less of the total damage, and this is often 

 equalled, and sometimes exceeded, by the loss caused by the diminu- 

 tion of weight of the sound seeds or the non-development of other 

 seeds. In the samples examined the average damage done has been 

 roughly proportionate to the percentage of bolls attacked, the loss 

 being somewhere about one-fifth of the total amount that could 

 have been produced by the infested bolls. This would give about 

 20 per cent, loss if all the bolls in a sample were attacked. In an 

 experimental field the damage done was between 11 and 16 per cent, 

 of the first picking and between 17 and 20 per cent, of the second 

 picking. 



Since the appearance of P. gossypiella it is noticeable that Earias 

 insulana (spiny boUworm) has almost disappeared as a major pest, 

 probably owing to legislation that has made conditions unfavourable 

 to its development. The bolls that were previously attacked by it 

 were destroyed to a much greater extent than those now infested by 

 P. gossypiella. It is true that the latter pest has compelled earher 

 cleaning up of the fields and has nearly done away with the possibiHty 

 of a third picking. This however was bound to follow the introduction 

 of early maturing varieties, which was necessitated owing to former 

 boUworm attacks being chiefly on the second and third picking. 

 The presence of P. gossyjneUa has accentuated this demand, and if 

 a still earlier maturing cotton can be developed, it will compete advan- 

 tageously with all later maturing varieties. 



From observations made in 1917-1918 the rate of increase of 

 P. gossypiella is shown for the various provinces. An attempt has been 

 made to solve the problem whether resting larvae feed. From a table 

 showing successive weighings of hibernating larvae a decided loss in 

 weight is noticeable ; this does not necessarily prove that the larvae 

 were fasting, but lends a measure of probability to the theory that 

 they do so. 



An examination of seed stores in Alexandria showed very few 

 moths flying in the day-time, though many were found hidden in dark 

 crevices. In a trapping experiment in a store a 25-candle-power 

 electric lamp was suspended about 6 in. above a basin of water with a 

 small quantity of paraffin oil on the surface. The fact that 54,000 

 moths were thus caught by trap -lights during the year sufficiently 

 disproves the statements that have been made that the adults are not 

 attracted to light. The largest nimibers were taken in September, 

 October and November, while from December to April very few were 

 observed. 



The results of treating the seed by heat have been observed in six 

 ginneries in Upper Egypt, and the germination records of seed so 

 treated are shown in a table. In view of the perfect results obtained 

 with seed treated at 150° to 157° F. as to germination and more especially 

 as to the greater safety in worm killing, it is considered advisable in 

 future for ginners employing heat treatment to work their machines 

 for temperatures of 140° to 150° F. rather than for 132° to 140° F. 

 The undesirabihty of exporting large quantities of treated seed to 

 countries where P. gossypiella is not yet established is commented 

 upon. Such cotton ought to be exported in small quantities only 

 and consigned in such a way that subsequent re-infestation of the seed 

 is made impossible. For instance, properly fumigated postal samples 



