November 2, 1896.] 



KNOWLEDGE. 



2o9 



THE LEAF-CUTTING BEE. 



By Francis M. Duncan. 



THE leaf-cutting bee (Meijachile rentunnilari^) is by 

 no means a remarkable looking insect, and from 

 its bumble exterior no one would imagine it to be 

 gifted with a higb sense of intelligence ; it does, 

 bowever, display a surprising amount of ingenuity 

 in the construction of the cells in which it places its eggs. 

 These bees are black in colour, with reddish hairs on 

 the thorax, and white down upon the head. They are 

 somewhat smaller than the hive bee, and are to be seen 

 in most gardens during the summer months busily 

 engaged cutting rose-leaves with their strong four-toothed 

 mandibles. 



The bee burrows a hole in the ground or in decaying 

 wood, forming a tunnel in which to place the cells ; it then 

 flies away to the neighbouring rose-bushes, and, selecting 

 a leaf, cuts a portion from it, which it carefully rolls up 

 and flies off with to the burrow. This mano'uvre is 



repeated several times, until ten or twelve pieces have 

 been cut ; the bee then enters the tunnel, and begins to 

 twist and fold the leaves, making them fit together into a 

 sort of funnel-shaped cone, something like a thimble. So 

 perfectly are these cells constructed, that they may be re- 

 moved from the burrow without falling to pieces, although 

 the leaves of which they are made are neither sewn or 

 gummed together. 



As soon as the cell is finished, the bee proceeds to make 

 a cake of honey and pollen, on which the future inhabitant 

 will live. It then lays an egg beside the cake, and H ies off to 

 find another leaf wherewith to close the entrance of the cell. 



A circular piece is cut from a leaf, and the bee flies 

 home with it, and so nicely has this little circle been cut 

 that it exactly fits the opening, into which the bee pushes 

 it, closing the cell completely. So that there may be no 

 fear of any honey leaking out, the bee flies ofl' again and 

 cuts two more circular pieces from the rose-bush, which it 

 fixes securely over the first one. When this cell is finished 

 a second is constructed which joins the first, so eight or 

 ten cells are usually to be found together in one burrow. 

 When all is finished the leaf-cutter closes the perpendicular 

 shaft leading to the burrow and llies away. 



The larva, when full grown, spins a silken cocoon within 

 and united to the sides of the cell. 



The illustration shows the nest of a leaf-cutting bee 

 found in the decayed wood of an old gatepost ; one of the 

 cells has been placed in an upright position to show its 

 compact and thimble-like form. 



WAVES.-XI. 



THE SEA OF ETHEE. 



By Vaughan Cornish, M.Sc. 



FAR away in the ether the sun is a storm centre, 

 ever creating waves which beat upon the earth 

 as the waves of ocean beat upon our coasts. 

 The much-soimding sea is silent save where the 

 billows break; so, too, the ocean of ether is cold and 

 dark, but its waves give light and heat when they beat 

 upon the earth. 



A mirror shining in the sun gives back his light and 

 gets but little warmth. The dark, rough surface of the 

 soil, which gives back Uttle light, grows warm in the sun's 

 rays. The mirror, like the vertical face of a stone pier 

 built out into deep water, prevents the waves from 

 breaking and reflects them back upon their path. A dark 

 surface acts like the dead resistance of the beach, absorbing 

 nearly all the energy of the waves and giving but little 

 back. The energy which was in the wave, changed in 

 form, becomes the warmth of the dark body. In the ether 

 the wave travels smoothly on, each part of the elastic 

 medium taking up the motion as the pulse arrives, and in 

 one complete swing passing on all the energy to the next 

 part, returning itself to rest — ready, however, to take up 

 the motion of the next oncoming pulse. The wave-length 

 of light is simply the distance between two pulses ; there 

 is no physical connection due to lagging of energy behind 

 the wave as in the wind waves of the sea, and if the sua 

 be screened or a flame be extinguished the ether does not 

 glow. 



If the pulses of ether follow one another somewhat 

 slowly, they excite our eyes so as to produce the sensation 

 of redness. If the pulses succeed each other more and 

 more quickly, the sensations are those of yellow, green, 

 blue, and violet. If the pulses follow one another at still 

 shorter intervals, the light passes slowly into darkness. 

 So, also, sound pulses succeeding one another too quickly 

 are not heard. Our organs of sense, " beautifully 

 delicate," as we like to call tliem, are too coarse to detect 

 the minuter ripplings of air or ether ; neither does the 

 scope of our vision enable us to detect those pulses of 

 ether which follow each other at comparatively great 

 distance, any more than the eye can distinguish the long, 

 flat billow which we call the flood tide. The widely 

 separated pulses of ether are, however, detected by their 

 warming power. The pulses of ether which succeed one 

 another more rapidly have generally httle warming 

 power, their energy being comparatively small. The 

 effects they produce resemble those of rapid tremors or 

 jarring. They shake things to pieces— not big things 

 which swing slowly, but such things as molecules, which 

 vibrate in about the same time as the interval between 

 two pulses. 



It seems that every body of which we know anything — 

 at any temperature which we have ever reached — is always 

 disturbing the atmosphere of ether in which all things 

 are immersed : for every body is warmed by the mere 

 neighbourhood of a warmer body. This occurs even when 

 the warmer body is nearly at the lowest temperature of 



• The evidence of nn etlu-r is dealt with in Chapter XIII. of my 

 "Short Stiulioi in Plivsioal Si-ienco." 



