3i6 THE WONDERS OF INSTINCT 



and weeks, if need be. Nothing worth remarking can 

 escape me. 



The caterpillars graze placidly, heedless of their terrible 

 attendants. If some giddy-pates in the turbulent swarm 

 pass over the caterpillars' spines, these draw up their 

 fore-part with a jerk and as suddenly lower it again; 

 and that is all: the intruders forthwith decamp. Nor 

 do the latter seem to contemplate any harm: they re- 

 fresh themselves on the honey-smeared strip, they come 

 and go tumultuously. Their short flights may land 

 them, now in one place, now in another, on the browsing 

 herd, but they pay no attention to it. What we see is 

 casual meetings, not deliberate encounters. 



In vain I change the flock of caterpillars and vary 

 their age; in vain I change the squad of parasites; in vain 

 I follow events in the jar for long hours, morning and 

 evening, both in a dim light and in the full glare of the 

 sun : I succeed in seeing nothing, absolutely nothing, on 

 the parasite's side, that resembles an attack. No matter 

 what the ill-informed authors say — ill-informed because 

 they had not the patience to see for themselves — the 

 conclusion at which I arrive is positive: to inject the 

 germs, the Microgaster never attacks the caterpillars. 



The invasion, therefore, is necessarily effected through 

 the Butterfly's eggs themselves, as experiment will prove. 

 My broad jar would tell against the inspection of the 

 troop, kept at too great a distance by the glass enclosure, 

 and I therefore select a tube an inch wide. I place in 

 this a shred of cabbage-leaf, bearing a slab of eggs, 

 as laid by the Butterfly. I next introduce the inmates 



