282 DR. L. H. GOTJGH. 



Egyptian cultivators have not yet quite realised that conditions have been changed 

 by the advent of the pink bollworm, and that they will have to reckon with it in the 

 future as a constantly recurring factor. On account of this pest the days are past 

 when, given suitable weather, pickings could be obtained in December or January. 

 Nowadays after October practically all the bolls matured are infested by the insect 

 in its most dangerous form, the long-cycle larva ; on account of this the longer the 

 crop is left standing, the greater the number of " resting " larvae produced and the 

 greater the probable attack in the next season. Given the same efficiency of the 

 campaign in the middle of October or the middle of December, the probable attack 

 of the next year's crop may be slight in the first case or intense in the second. 



To sum up, it appears to us that in addition to the thoroughness in cleaning up 

 the land and destruction of resting larvae, earliness in the production and removal 

 of the crop and earliness in the application of the control measures are essential. 



Problems Connected with the Pink Bollworm. 



It is extremely difficult when dealing with an insect which, like the pink bollworm, 

 passes its whole larval existence safely hidden away in the interior of a green cotton- 

 boll or of a cotton seed, to produce much direct evidence of its life-history or habits. 

 The larva of Gelechia resents any interference with itself or with its habitation. 

 Removed from its boll or seed it immediately reacts in some way, probably normal 

 to the circumstances, but not normal to the insect if left alone. The conviction 

 is gaining on the writer that the length of a life-cycle is materially altered by such 

 interrruptions as the picking of a green boll containing a Gelechia larva, the breaking 

 open of a " double " seed containing a larva, and by the operations of ginning and 

 even by the transport of seeds or bolls containing pink bollworm. 



In these circumstances one is forced to obtain evidence to a great extent by indirect 

 methods, which are not very frequently used in Entomology, hoping later on to verify 

 by direct observation the theories that massed figures have led one to adopt. 



In this paper an attempt has been made to apply statistical methods to various 

 problems connected with Gelechia, the principle ones being the rate of increase, the 

 amount and nature of the damage done by the insect to the crop, and certain features 

 of the life-history which are best studied in this way. 



The Rate of Increase of Gelechia damage in Egypt since 1911. 



Prior to 1910 no records are available of the existence of Gelechia gossypiella in 

 Egypt. The first specimens taken appear to have been those collected by 

 Mr. F. C. Willcocks, in bolls received from Damanhur and Mansura, and by Mr. Adolf 

 Andres, near Mansura, in the autumn of 1910. In the autumn of 1911 a few were 

 bred by the present writer from cotton bolls collected at Fua and Dekernes, and in 

 March 1912 a few specimens of larvae and pupae were received by him in cotton 

 seed sent from Damanhur by Mr. Pappis (see also Willcocks, " The Pink 

 Bollworm," p. 8). 



The first serious outbreak of Gelechia took place on Abu Kir Estate, near Alexandria, 

 in the autumn of 1912 ; since then the insect has established itself as a major pest 

 throughout Egypt. 



