250 INSECTS AND MAN 



bugs ; termites, the so-called " white ants," which may be 

 classed as noxious insects, are captured and killed at every 

 opportunity. Sorghum midges, Contarinia sorghicola, in- 

 veterate enemies of sorghum, maize, etc., find their greatest 

 natural enemy in the Argentine ant ; whilst its action, in 

 destroying other ants, assumes either a beneficial or an 

 injurious aspect according to whether the annihilated 

 ant is itself beneficial or injurious. 



The Argentine ant is gregarious, living in colonies com- 

 prised of females or queens, males (fig. 68, A) and workers. 

 There are no major and minor workers and no special scouts 

 or soldiers, such as occur in some other ant colonies. The 

 females (fig. 68, B) are 4*5 to 5 millimetres, the males 2'8 to 

 3 millimetres, and the workers 2*2 to 2'6 millimetres in 

 length ; all are dark brown, nearly black, in colour. The 

 white elliptical eggs have a pearly lustre, and the very 

 delicate and thin shells are mucilaginous, so that they 

 adhere to one another. On this account they can be de- 

 posited on the walls and ceilings of the ant's dwellings, and 

 can, when necessary, be handled en 'masse by the workers. 

 When the eggs are about to hatch they become less lustrous, 

 quite dull in fact, and they frequently assume the general 

 contour of the contained larvae, making it very difficult 

 to distinguish between such eggs and newly hatched larvae. 

 In specially constructed cages, where the ants can be kept 

 under observation, it is interesting to note the great care 

 which the workers (fig. 68, c) take of the eggs, in order to 

 secure the proper amount of humidity. Now the workers 

 are piling up the eggs in one corner of their cage, now col- 

 lecting them in the centre, next, may be, they will be moved 

 to another compartment altogether or stuck to the ceiling. 

 Many times a day, in fact, is their position changed by 

 the assiduous workers, and sometimes eggs and pupae are 

 carefully separated; at other times they are jumbled to- 

 gether in seemingly hopeless confusion. This care of the 

 eggs by the workers appears to be absolutely essential to 



