HARDWICKE'S SCIEN CE- GOSSIP. 



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Crag in Belgium, but these are often hardened into 

 stone. They may, and perhaps are, somewhat 

 older than those we have been attempting to de- 

 scribe, and may lie regarded as connecting the 

 Miocene with the Pliocene period, just as the last- 

 mentioned crag-bed connects the latter epoch with 

 the Glacial. We have ample proofs that this Bel- 

 gian bed extended across the German Ocean into 

 Suffolk, where it was broken up, and the fragments, 

 rolled and angular, are often found in abundance at 

 the base of the Red Crag, and known by the local 

 name of "Box-stones." 



In Sicily beds of Pliocene age abound, and have 

 been uplifted to 3,000 feet above the sea-level 

 since the time when the Norfolk and Sulfolk beds 

 were formed. Many of the shells spoken of, which 

 migrated from English latitudes during the later 

 Pliocene, and when the cold was increasing, took 

 up their habitats in Sicilian seas, and are now found 

 fossilized in the limestones. Since then their de- 

 scendants have returned to their original English 

 home, and, as the oyster and mussel, administer to 

 modern English appetites. The oldest of these 

 Sicilian beds, perhaps contemporaneous with the 

 Coralline Crag, was strewn over an area that was 

 subject to volcanic shocks. Occasionally volcanic 

 ashes were intercalated with the shell marl. At 

 length, by the simple accumulation of volcanic 

 ashes and lava, during a slow elevation as well, a 

 great mountain 11,000 feet in height was formed ! 

 That mountain was Etna, and the Pliocene shell- 

 beds at the height of 1,200 feet along its flanks indi- 

 cate its recent origin. In Italy, just above Biorence, 

 there was a great fresh-water lake, into which the 

 rivers occasionally carried carcasses of mastodons, 

 elephants, &c. The deposits which formed along its 

 bottom accumulated to 250 feet in thickness. All 

 over the Northern hemisphere great zoological as 

 well as physical changes occurred during the period 

 of the " Crags." Animal life slowly prepared for that 

 great event which wrapped Europe in glacial ice for 

 tens of thousands of years. All these facts may be 

 more or less accurately and minutely read off in the 

 sometimes loose and unconsolidated strata of the 

 Pliocene age, of which we Crag-beds are the English 

 representatives. 



ANTS AND THEIR SLAVES. 



ff^HERE are two species of ants which are accus- 

 -■- tomed to make predatory incursions for the 

 purpose of carrying off the larva: and pupa? of their 

 black brethren,— Polyergits rufescens and Formica 

 xanguuiea. As neither of these ants arc natives of 

 Britain, we have not the opportunity of watching 

 their habits for ourselves ; and, under these circum- 

 stances, I venture to think that a short account of 

 their expeditions will not be uninteresting to the 

 readers of Science-Gossip. The predatory ants 



do not leave their nests for these incursions till the 

 male insects are nearly ready to emerge, and then 

 they send out scouts, who run over the adjacent 

 fields in search of a nest of ncgro-ants ; or if these 

 are not to be found, they look out for some other 

 species, such as the miners (F. citrucularia), though 

 these latter are very courageous. Huber says of 

 them : " These ants will fight with the most obsti- 

 nate courage, scarcely yielding an inch. In fact, 

 as soon as their assailants are in sight, myriads of 

 miners rush upon them with great fury, and the 

 nest becomes the scene of a terrific conflict ; and 

 though the red ants are larger in size, and usually 

 number more than the miners, they are often beaten 

 off by the latter." But to return. When the 

 scouts come back to the nest, active preparation is 

 made for the impending expedition, and the war- 

 riors who are destined to take part in it are selected. 

 The ants now get so excited that they butt at each 

 other witli great violence, and let out their exuber- 

 ant spirits by cleaning their legs and antennae, and 

 by general and ceaseless activity. On the following 

 day, about four o'clock, the chosen band sallies 

 forth, being preceded by an advanced guard of a 

 dozen ants, who march before the main body for 

 about a yard, and then wheel round and take their 

 place at the rear, their former position being occu- 

 pied by the front rank of the main body, who fall 

 back in their turn, and are replaced as before. Thus 

 they march until they approach the negro camp, when 

 they separate, each ant pursuing a devious course 

 through the grass, and coming suddenly on the formi- 

 cary, which is frequently left unguarded. In gene- 

 ral, the black ants make no attempt to defend their 

 progeny, but beat a precipitate retreat from one 

 side of the nest as the plunderers enter the other. 

 Occasionally, however, a fight takes place, in which 

 the negroes are invariably vanquished, being placed, 

 at a disadvantage and terror-stricken by the sudden 

 nature of the attack. After the battle the pupae 

 are transported to the nest of their captors, where, 

 however, they suffer no diminution of happiness, 

 being brought up and employed in the same way as 

 they would have been in their own home. The 

 motive which induces the rufescent ants to make 

 these excursions is their excessive indolence. The 

 negro slaves do all the work, even feeding and 

 carrying about their masters, and not unfrequently 

 obtain such an ascendancy over them as to reverse 

 their respective positions. Eor instance, they will 

 not allow them to go out on their expeditions before 

 the proper time ; and if they return without their 

 usual booty, the negroes show their displeasure by 

 attacking them and preventing their entry into the 

 nest. Kirby and Spence, in their " Entomology," 

 say that the rufescent ants, in addition to the 

 pupae, carry off prisoners, whom they ultimately 

 devour. But this is doubtful. 

 Blackheath. E. C. Lefroy. 



