266 INJURIOUS INSECTS 



backs of the plant-lice. They were so small as to be 

 scarcely visible to the naked eye, but a good lens soon 

 helped me to see what they were doing. They were busy 

 depositing eggs in the "ant's cows!" The Ichneumon 

 would mount the back of a " cow/' when the latter would 

 become restive and try to dismount its rider by kicking 

 and nearly standing on its head, and this would set the 

 others next it to kicking in the same way, until all on 

 the leaf seemed to be panic-stricken, and were kicking, 

 striking, and throwing themselves about in a most ludi- 

 crous manner, all the while holding on by their beaks. 

 And it was very amusing to see the excited ants trying 

 to find the cause of the panic. But the little Ichneu- 

 mons did not " seem to be in the least disconcerted and 

 did their work most effectually as the sequel proved. 



Not many days after I witnessed the egg-laying, the 

 abdomens of the plant-lice were very much distended, and 

 they no longer gave any nourishment to the ants, who 

 passed around among them as if discouraged. Two ants 

 would meet and seem to consult over the matter, then 

 they would stroke the " cows" with their antennae, but 

 meeting with no response they would pass to another 

 leaf, with no better result. At last they tried to remove 

 the " cows," they would take them gently in their mandi- 

 bles, but in many cases the beak was inserted so firmly in 

 the leaf or twig they could not remove it. When they 

 did succeed in removing one they invariably carried it to 

 the nest. 



This was the most complete destruction of plant-lice I 

 ever witnessed. I could not find a single living speci- 

 men left. In due time a little shining black Ichneumon ~ 

 fly the counterpart of its mother emerged from a hole 

 in the back of each aphis. 



Since my observations were made on this orange aphis 

 it has been named by Mr. Ashmead, SipJionophora citri- 

 folii, and the little Ichneumon has been named by Mr. 



