NATURALIST AT LARGE 



Golden Tomb Fit for a Queen 



Ancient ants preserved in amber show that the insects 

 have farmed mealybug "cattle" for at least 15 million years. 



Ancient amber from the Dominican Republic, between 15 and 20 million years 

 old, preserves the fossil of an ant queen (Acropyga glaesaria) on her nuptial 

 flight. In her mandibles the ant clutches a small mealybug (Electromyrmoccus 

 reginae), whose progeny would have produced food for the new ant colony 

 the queen might have founded. Instead, both insects became stuck in tree 

 resin and then entombed as the resin turned to amber. The ant's behavior — 

 dubbed trophophoresy ("carrying food") — still occurs in modern species of 

 Acropyga. The image is magnified 45X. 



By John S. LaPoila 



Let's travel far back in time to a 

 clear, sunny morning between 

 1 5 and 20 million years ago in a 

 tropical Caribbean forest. A gentle rain 

 the night before has softened and 

 moistened the ground. Out through 

 the warm, loose earth a small worker 

 ant pokes her head and, for the first time 

 in her life, gazes on the sunlit world. 

 She dislikes the light and would nor- 

 mally shun it, but today she puts up 

 with it in order to clear a small open- 

 ing. Several of her sisters are emerging 

 nearby, also digging small holes that link 

 their underground nest to the outside 

 world. When their work is complete, 

 the workers scurry to the safety of their 

 dark home. For a few minutes, all is still. 



Then, dozens of virgin winged 

 queens and males crawl out of the same 

 holes. Stretching their wings, the re- 

 productives — as queens and male ants 

 are collectively called — make their way 

 up the stems of plants and the sides of 

 small rocks to reach the highest points 

 they can. From there, they take flight. 



Such an event actually took place 

 during the Miocene period, on what 

 today is the Caribbean island of His- 

 paniola. Once the ants mated, the 

 luckiest few among the queens — the 

 ones not killed in accidents or through 

 predation — started new colonies. As 

 for the males, their goal in life was 

 complete, and they soon died. 



Nuptial flights continue to this day 

 among ants. In North America they of- 

 ten take place from spring through fall, 

 an event that many anxious homeown- 

 ers mistake for an invasion of house- 



ravaging termites. But there was some- 

 thing special about the flights millions 

 of years ago, something shared by only 

 a few groups of ants today. When the 

 queens took off. each one held a small, 

 white mealybug in her mandibles, a rare 

 ant behavior I have termed trophopho- 

 resy (meaning loosely, "carrying food"). 

 The mealybugs held by the queens be- 

 came the ancestors of herds of mealy- 

 bugs (the ants' "cows") that would be- 

 come "corralled" in each new ant 

 colony, providing the ants with food. 



But not all the ancient queens 

 reached their new homes. Some repro- 

 ductives met their demise when they 



ventured too close to a species of algar- 

 robo tree — Hymenaea protera — and be- 

 came trapped in its sticky resin. How- 

 ever unfortunate the entrapment 

 proved for the queens and the mealy- 

 bugs they carried, it turned out to be 

 good news for modern biologists. In the 

 millions of intervening years, the resin 

 turned into amber, and the ants en- 

 tombed in the amber became fossils. 

 Time seemed to have stopped around 

 them, until one day their remains were 

 discovered in a Dominican amber mine. 



As it happens, a few years ago I ex- 

 amined a fossil of one ant queen and 

 her mealybug in a piece of amber and 



6 



NATURAL HISTORY May 2006 



