132 BR. J. ENT. NAT. HIST., 6: 1993 



Table 2. Details of ladybirds which successfully ate aphids. Results are only for carnivorous 

 ladybird species. 



(1) On the colony two of 52 ladybirds (4%) ate an aphid from a colony tended 



by ants. 



five of nine ladybirds (56%) ate an aphid from the colony 

 not tended by ants. 



five of 52 ladybirds got hold of an aphid but had it retrieved 

 by the ants. 



(2) Away from the colony five of 52 ladybirds (10%) ate an aphid away from the colony. 



one of 52 ladybirds got hold of an aphid away from the 

 colony but had it retrieved by ants. 



(Aphids away from the main colony were either winged individuals walking on the leaves of 

 the plant or sessile individuals feeding away from the colony). 



Note: 26 ladybirds out of 52 reached the colony. 



The results for the 'ladybird success rate' (see Table 2) show the enormously reduced 

 success rate of ladybirds when the aphids had ants in attendance, compared with the 

 control colony. 



In order to determine the nature of the stimulus that induces ants to attack, a 

 'pseudo-ladybird' was made out of Blu-Tack and coloured red and black. This was 

 stuck onto the thistle to see how the ants responded. It was totally ignored by the 

 ants, even when an aphid was squashed in the process of putting it onto the plant. 

 This suggests that it is either the movement of the ladybird or a chemical stimulus 

 from the ladybird that provokes the attack and not just the presence of a foreign 

 body on the aphid colony. 



Table 3. Summary of results of experiment for all ladybird species, including non-carnivores, 

 combined. 







Larvae 



Adults 



Control 



Reaches aphid colony 





5 



31 



6 



Encountered ant(s) 





8 



44 



— 



Ant grabbed ladybird 





2 



6 



— 



Ant squirted acid 





1 



8 



— 



Ladybird dropped off 





2 



9 



— 



Ladybird clamped down 





— 



8 



— 



Ladybird returned to colony 





— 



5 



— 



Ladybird flew off 





— 



22 



1 



Ladybird stayed away 





6 



27 



4 



Ladybird ate an aphid on colony 







2 



5 



Ladybird ate an aphid away 



from the colony 



2 



5 







Total individuals used 





12 



67 



9 



