ALIEN ASSOCIATES AND AFFINITIES 



may apply Marlowe's phrase: "Infinite riddles in a little 

 room." It has taken the patience, skill, and experience 

 of the trained naturalist to trace it and unfold it to us. 

 But it needs no expert to note the admirable adaptations 

 by which a minute fly has been borne on, step by step, 

 in utter helplessness, through the successive stages of a 

 dependent being, from a mere speck of vital matter to a 

 winged insect, armed with the instinct to invade an un- 

 unknown world and propagate its kind. How great 

 and how infinitely exact must be that Over-Force that 

 dominates nature, which can include within the compass 

 of laws that regulate the universe a series of adaptations 

 like these which guard the life of a two-millimetre para- 

 sitic fly! It amazes, while it perplexes one, to account 

 for it all. Yet, in the face of great Nature's workings, 

 one may venture to recall the proverb of Spenser (not 

 Herbert, but he of the Faerie Queene) : 



' 111 can he rule the great who cannot reach the small." 



In contrast with our studies of the chalcid Orasema 

 viridis and the beetle Xenodusa cam, it is pleasing to 

 record that the association between Metopina the fly 

 and Pachycondyla the ant is apparently wholly benign 

 at least, under ordinary conditions. The guest does not 

 prey upon its host; no physical injury seems to follow 

 its enforced companionship; and the bare particle of 

 food filched from the ant larva does not tax the supply- 

 department of the commune or cause its workers to 

 stint their own dependents. The larval hosts them- 

 selves are as large and healthy as others in the nest, and 

 produce normal pupae. It is a case of "all's well that 

 ends well." 



These are but types of numerous examples of those 



241 



