BIOLOGIC BELATIONS BETWEEN PLANTS AND ANTS. 425 



If the flower lias 110 stiff or viscous protecting Lairs, if its peduncle 

 is neither glaucous nor steep, it adopts various devices for the purpose 

 of protecting its floral nectaries against ants — devices that afl'eet various 

 organs. In certain narcissuses the tube is so narrow that an ant can 

 not enter. Only the proboscis of a winged insect can penetrate it. In 

 the Campanula the flowers are widely open, but the stamens are so 

 united as to form a sort of box, in which the nectar is found. Bees are 

 very early risers, while ants do not go ont until the dew is off. A flower 

 which possesses no means of protection against ants has, therefore, an 

 advantage if it opens early in the morning and closes its corolla before 

 the ants arrive (Lubbock). Thus it is that the flowers of the Tragopogon 

 pratense close early in the morning. Those of Lampsana comm unis and 

 of Crepis pidclira open before 6 o'clock and close about 10 o'clock a. m. 



The nectar-producing plants of England are generally pubescent. 

 Lubbock has drawn up a list of 110 species that are nectariferous and 

 smooth. In GO of these the passage leading to the nectar is so narrow 

 that the ant can not pass. Thirty are aquatic, 3 or 1 open only at night, 

 6 grow in the open ground but are very small, so that to them hairs 

 would be of very doubtful utility. 



In a number of cases the ants borrow the nectar from vegetables 

 through the intermediation of animals. A true animal honey dew is 

 secreted by plant lice {Aphides) or cochineal insects (Goccidce). It is 

 well known that these insects excrete from the posterior extremity of 

 their digestive tube a saccharine liquid of which the ants are fond. 

 Upon the leaves covered with aphides ants constantly circulate, and, 

 tickling these creatures upon the abdomen with their antennae gather 

 the sugary drops that are then exuded. The adaptation of these 

 aphides to the ants is so perfect that, according to Darwin, when one 

 is tickled by a hair it will not give up its liquid, that result only follow- 

 ing tlie excitation produced by the ant (?). However this may be, 

 aphides and sometimes cochineal insects are truly purveyors to the 

 ants. Linnaeus called them Vaccce formicarum, or ant-cows. 



The habits of these pastoral ants are too well known for us to dwell 

 upon them, but it is well to remember that there are, so to speak, two 

 degrees of complexity in the relations of these insects. Many ants are 

 content with collecting the nectar from the aphides in the open air, 

 others construct covered ways and regular aerial stables to j)rotect 

 their "cows" from the attacks of their enemies and to "milk" them at 

 their ease. 



Sometimes, also, when the aphides frequent the subterranean parts 

 of vegetables, they construct underground stables. In our country the 

 aerial stables are temporary, made of loose earth and fragile, but Osten- 

 Sacken has seen, near Washington, a branch of juniper carrying an 

 aerial stable formed of agglomerated filaments having a resinous odor. 

 He has even seen in Virginia an aerial stable, spherical but fragile, con- 

 structed upon an Asclepias. Trelease has also seen in North America 

 aerial stables established by Crematogasters upon Andromedas. 



