78 



KNOWLEDGE 



[Apbil 1, 1892. 



Fig. 5. — Queen of Lep- 

 tothorax acervorum, 

 depriTed of wings. 

 A burrower under 

 bark. Magnified 8 

 diameters. 



deposits are gradual, grain by grain, 

 they do not prevent the continued 

 growth of the grass, which is ever 

 extending itself outward, forming an 

 excellent thatch and acting as an 

 efficient watershed in case of rain. 

 The insect can, however, adapt itself 

 to circumstances, and in hilly country 

 where grassy mounds are impossible 

 will avail itself of the protection 

 afforded by loose fragments of rock. 

 The Eed Stinging Ants {Mi/nnica) 

 similarly excavate the ground imder 

 stones, while a neat little reddish 

 species called Le}>tothora.r arervonun 

 (Fig. 5) forms galleries under the 

 bark of trees, especially fir stumps. 

 Lastly may be mentioned a thin 

 and wiry small black species, the 

 workers of which have a squarish head 

 which is streaked with longitudinal 

 furrows ; it is called Tetrumorium ciespitum (Fig. 6), 

 and is foimd at various places 

 along our south-eastern coasts, 

 seeming for some reason or other 

 to prefer to be near the sea. It 

 also shams death when disturbed, 

 folding up its legs and lying quite 

 still. We have thus seen that 

 the lives of the worker Ants in 

 all these latter species are spared 

 much of the labour which falls to 

 the lot of the mound-builders, and 

 whatever journeys are undertaken 

 will be, not for the accumulation 

 of building material, but only for 

 obtaining food. 



Ants feed chiefly upon insects 

 of various kinds, honey, honey- 

 dew, and fruit, and for a large 

 nest the daily bill of fare must be 

 extremely varied and comprehen- 

 sive. In nests of only moderate 



size, the number of individuals will run up to thousands, 

 while of very large ones Sir John Lubbock's opinion 

 is that " perhaps London and Pekin are about the only 

 human cities which can compare with them " as to 

 population. The amount of food that such multitudes 

 would daily need is difficult to conceive, but so far at 

 least as animal food is concerned, the requirements of 

 a large nest would probably demand that many thousands 

 of small insects of different kinds should be slaughtered 

 every day. The hunting and gathering in of this quarry 

 is largely left to individual enterprise, at least amongst 

 the species found in this coimtry, no organized foraging 

 parties being usually employed ; possibly, however, certain 

 special individuals may be sometimes told off for the 

 work. The corpse of a larger insect, such as a good- 

 sized beetle or a bumble bee, is an excellent find ; if too 

 large and heavy to be di-agged to the nest in its enth-ety, 

 even by the united efforts of a gang of labourers summoned 

 by commimications from the original discoverer of the 

 booty, the carcase must be cut up where it lies and carried 

 home piecemeal, an operation not difficult of accomplish- 

 ment by insects that always carry in their mouths a good 

 pair of scissors in the form of mandibles. The collection 

 of honey-dew leads many Ants to climb trees and plants, 

 and wander over their leaves in search of the deposit, or of 

 the aphides which produce it. 



Fig. 6. — Tetramorinm cces- 

 pitum. Worker. A sea- 

 coast Ant. Magnified 10 

 diameters. 



THE FACE OF THE SKY FOR APRIL. 



By Herbert S.^dler, F.R.A.S. 



LARGE groups of spots and faculse continue to 

 diversify the solar surface. There will be a total 

 eclipse of the Sun on the evening of the 26th, 

 but as it will not be visible in the northern 

 hemisphere, it need not be further noticed here. 

 The following are conveniently observable times of some 

 Algol-type variables (</. " Face of the Sky " for March). 

 S Cancri. — April 3rd, llh. Im. p.m. ; April 22ud, lOh. 17m. 

 P.M. 8 Libr;B.— April 6th, lOh. 12m. p.m.; April 13th, 

 9h. 46m. P.M. ; April 20th, 9h. 10m. p.m. ; April 27th, 

 8h. Sim. p.m. U Coronie. — April 5th, llh. 28m. p.m. ; 

 April 12th, 9h. 10m. p.m. 



Mercury is an evening star during the first of the month, 

 and is well placed for observation during the beginning of 

 April, in the sense of setting some considerable time after 

 the Sun. His brightness, however, has notably diminished 

 since the third week in March. On the 1st he sets at 

 8h. 30m. p.m., just two hours after the Sun, with a northern 

 decUuation of 14° 24', and an apparent diameter of 7|", 

 ^ijths of the disc being illuminated. On the .5th he sets 

 at 8h. 31m. p.m., or Hi. 52m. after sunset, with a northern 

 declination of 15° 3!)', and an apparent diameter of 8^", 

 j^ths of the disc being illuminated. On the 10th he sets 

 at 8h. 16m. p.m., or about Ij hour after the Sun, with a 

 northern declination of 15° 55', and an apparent diameter 

 of lO'O", jijtli of the disc being illuminated. After this 

 he rapidly approaches the Sun, being in inferior con- 

 junction with him at 4 p.m. on the 19th. He describes, 

 while visible, a very short arc in Aries, without approaching 

 any naked eye star. 



Venus is now a resplendent object in the evening sky, 

 being visible to the naked eye before sunset towards the 

 end of the month. On the 1st she sets at lOh. 51m. p.m., 

 4h. 20m. after sunset, with a northern declination of 

 21° 30", and an apparent diameter of 17f", T%%ths of the 

 disc being illuminated. On the 15th she sets at llh. 26m. 

 P.M., li-h. after sunset, with a northern declination of 

 24° 63", and an apparent diameter of 20-0". About 

 f^^ths of the disc are then illuminated, the brightness of 

 the planet being about frds of what it will be at the 

 beginning of .June. On the 30th she sets at llh. 49m. 

 P.M. (being at her greatest eastern elongation [45^°] at 

 5h. A.M. that morning), with a northern declination of 

 26° 46', and an apparent diameter of 22J", just one-half of 

 the disc being illuminated. At about 8h. 30m. p.m. on the 

 27th the planet will be J' north of a 9-1 magnitude star. 

 During the month she describes a direct path through 

 nearly the whole of Taurus, being closely south of the 

 Pleiades ou the evenings of the 2nd, 3rd, and 4th. 



Both Mars and Jupiter are, for the observer's purposes, 

 invisible. 



Saturn is an eveuuig star, and is very well situated for 

 observation. He rises on the 1st at 4h. 41m. p.m., with a 

 northern declination of 4° 3', and an apparent equatorial 

 diameter of 19-2" (the major axis of the ring system being 

 44-1" diameter and the minor 1-0"). On the 30th he rises 

 at 2h. 37m. p.m., with a northern declination of 4° 42', and 

 an apparent equatorial diameter of 18'6" (the major axis 

 of the ring system being 42-8" in diameter and the minor 

 0-4"). The following phenomena of the satellites may be 

 observed (the times are given to the nearest quarter of an 

 hour). April 7th, Ojh. a.m., Dione, eclipse reappearance. 

 April 9tli, 3ih. a.m., Rhea, eclipse reaj^pearance. April 12th, 

 Tethys, eclipse reappearance ; 9h. p.m., shadow of Titan 

 in central transit. April 14th, Ijh. a.m., Tethys, eclipse 

 reappearance. April 15th, lOfh. p.m., Tethys, eclipse re- 



