376 EVOLUTION AND ANIMAL LIFE 



to lick the face and the back of the head of each host. A 

 Myrmica thus treated, says Wheeler, 



"paused, as if spellbound by this shampooing and occasionally folded 

 its antennas as if in sensuous enjoyment. The Leptothorax after licking 

 the Myrmica's pate, moved its head round to the side and began to 

 lick the cheeks, mandibles, and labiuni of the Myrmica. Such ardent 

 osculation was not bestowed in vain, for a minute drop of liquid 

 evidently some of the recently imbibed sugar-water appeared on the 

 Myrmica's lower lip and was promptly lapped up by the Leptothorax. 

 The latter then dismounted, ran to another Myrmica, climbed on its 

 back, and repeated the very same performance. Again it took toll 

 and passed on to still another Myrmica. On looking about in the nest 

 I observed that nearly all the Leptothorax workers were similarly 

 employed." 



Wheeler believes that the Leptothorax get food only in this way. 

 They feed their queen and larvae by regurgitation. The 

 Myrmicas seem not to resent at all the presence of their Lepto- 

 thorax guests, and indeed may derive some benefit from the 

 constant cleansing licking of their bodies by the shampooers. 

 But the Leptothorax workers are careful to keep their queen 

 and young in a separate chamber, not accessible to their hosts. 

 This is probably the part of wisdom, as the thoughtless habit of 

 eating any conveniently accessible pupae of another species is 

 widespread among ants. 



There are numerous interesting cases of symbiosis in which 

 not different kinds of animals are concerned, but animals and 

 plants. It has long been known that some sea anemones 

 possess certain body cells which contain chlorophyll, that green 

 substance characteristic of the green plants, and only in few 

 cases possessed by animals. When these chlorophyll-bearing 

 sea anemones were first found, it was believed that the chloro- 

 phyll cells really belonged to the animal's body, and that this 

 condition broke down one of the chiefest and most readily 

 apparent distinctions between animals and plants. But it 

 is now known that these chlorophyll-bearing cells are micro- 

 scopic, one-celled plants, green algae, which live habitually 

 in the bodies of the sea anemone. It is a case of true symbiosis. 

 The algae, or plants, use as food the carbon dioxide which is 

 given off in the respiratory processes of the sea anemone, and 



