TRANSACTIONS OP SECTION D. 



209 



WEDNESDAY, SEPTEMBER 10. 



The following Papers and Reports were read : — 



1. Iridomermyx humilis : A Contribution to the Life History of the 

 Argentine Ant. By Dr. M. C. Grabham (communicated hy Dr. 

 F. G. Penrose). 



The author described the insidious introduction of this ant into ^Madeira, 

 its spread, and the complete suppression of competing species. It is established 

 in destructive colonies up to 2,500 feet above sea-level. Coffee cultivation is 

 ruined, and every sort of fruit tree — Citrus especially — which will support coccus 

 or aphis is almost entirely destroyed. Sugar-cane and bananas still exist, though 

 badly attacked ; sweet potatoes (Batatus) have disappeared in many districts, 

 a teeming population being thus deprived of a most important food. Every 

 house is invaded and every kind of food carried off, and there is no winter 

 weather to check the ant. Poultry, young birds, and bees are defenceless. 



The author pointed out the methods and ingenuity of the ant in food-search- 

 ing ; how the ant transplants its pupaj into favourable conditions, and makes 

 bridges to reach flies caught on sticky fly-paper. 



The females are mostly impregnated within the formicary, and immediately 

 afterwards shed their wings. Experiments show that the sense of smell is 

 predominant. Reference was made to harmony in working and to the singular 

 absence of fighting when separate communities meet. The ant's enemies are 

 few; spiders devour them and Pholcus fhalangmdes is a formidable enemy. 



One hope is in the eventual exhaustion and decreased fertility of the ant. 

 Methods of control — singular effect of chalk powder ; banding trees with rags 

 soaked in corrosive sublimate is efficient. 



By surrounding a lemon tree with a circle of powdered potassium cyanide 

 every ant in passing to or from the tree was killed, and it was found that 

 40,500 ants had been tending the scale-insects on this one tree. 



The progress of the ant in Madeira justifies American opinion that this pest 

 ie an agent of destruction as formidable as the Colorado beetle or the cotton- 

 boll weevil. Our colonies should be warned as to the importance of this pest. 



2. Sex Inheritance in Lice. By Dr. E. Hindle.* 



Pairs of body-lice were isolated and their offspring raised through five 

 generations, but of sixty families obtained, twenty-four were mixed — i.e., com- 

 prised both males and females — nineteen were female, thirteen male, and four 

 crosses were sterile. The three sorts of families occurred simultaneously, 

 although the lice were fed on the same individual and reared imder the same 

 conditions, and no explanation of their appearance could be discovered. The 

 proportion of females to males in the total number of adults raised to maturity 

 agreed almost exact/ly with that occurring in Nature (60 per cent, females, 

 40 per cent, males). 



From the three types of families, four kinds of crosses are possible, and the 

 results of a number of these are as follows : — 



1. 9 from a female family x S from a male family; 11 families; 2 female. 

 5 male. 3 mixed (18 ?? : 8<J^), 1 sterile. 



2. $ from a female familv x <? from a mixed family ; 7 families ; 3 female, 

 2 mixed (15?? : 2^<?(?) ), 2 sterile. 



3. 9 from a mixed family x <? from a male family; 11 families; 3 female, 

 7 mixed (33 $? : 61 c?c?), 1 sterile. 



4. ? from a mixed family x c? from a mixed family ; 3 families all mixed 

 (10?? : 19 <?(?). 



Different types of families were obtained by crossing the same female with 

 two successive males, and also by crossing the same male with two females, 

 these results suggesting the existence of two kinds of males and two kinds 

 of females. 



» See Journ. of Genetics, vol. 8, No. 4, Sept. 25, 1919. 



