Sept, 



1885.] 



♦ KNOV/LEDGE ♦ 



to walk by faith, and not by sight. The explanation -which 

 wc gave on p. 92 of Vol. VI. of the phases exhibited by 

 Venus is equally applicable, mutatis mutandis, to those 

 shown by Mercury, and the reader is requested to 

 refresh his memory by a re-perusal of what was said 

 in the place cited, for the better apprehension of 

 what is to follow. Mercury then attained his greatest 

 elongation west of the Sun (p. 231) at 7 p.m. on the 18th, 

 and hence, at the date of our observation, he was about 

 three days and a half from it. A glance at the figure 



will show tliat the illuminated portion of the planet 

 visible was decidedly smaller than it should theoretically 

 have been from the relative positions of the Sun, Earth, 

 and Merciiry. As may be imagined, however, some 

 attention is needed to detect this feature in so tiny a 

 crescent as the planet presents. The shading towards 

 the terminator, or apparent inner edge of the crescent, is 

 both considerable and ill-defined. Whether this has its 

 origin in the planet's atmosphere or not is by no means 

 easy to determine. The student, after scmtinising 

 Mercury, should turn his telescope upon Venus, the 

 brilliance of whose light stands out in striking contrast 

 to the comparatively feeble illumination of her inner 

 neighbour. Spots, streaks, Ac. (whence a hypothetical 

 rotation period has been deduced), and a blunting of at 

 least one of the horns of the crescentic planet have been 

 seen, either objectively or in imagination, by many obser- 

 vers; but, as we have hinted above, all such detail is hope- 

 lessly beyond the possessor of a small instrument. 



As in the case of Venus, when Mercury is in or near 

 either of his nodes at the time of inferior conjunction, 

 he passes across the Sun's disc — or, as it is technically said, 

 " Transits " the Sun as a black spot. With too light an 

 eye-shade he shows well the notorious ligament or black 

 drop (concerning which so much has been written in 

 connection with transits of Venus) at his entry on and 

 exit from the Sun's face. An aureola or luminous ring 

 round the black disc of the planet has also been seen 

 while it has been crossing the Sur ; while several 

 observers of skill and repute have seen one, and even two, 

 whitish spots on the dark disc of the planet itself under 

 the same conditions. These phenomena are quite within 

 the reach of such a telescope as that whose use we are 

 pre-supposing ; but, unfortunately, the student will liavc 

 to wait some time before attempting to verify such 

 observations as those which we have just described, inas- 

 much as only two more Transits of Mercury will occur 

 during the present century : the first happening on 

 May 9, 1891, and the next on November 10, 1894. 



At tlio Royal Arsenal, Woolwich, on Tuesday week, a tank con- 

 tainiiiK several thousand gallons of oil took lire. It was the oil in 

 which the tubes for the steel guns was tempered. All that could be 

 i\otn: was to remove and extinguish the burning wooden covers, and 

 to at once close down the boiling fat with sheets of iron covered 

 with ashes. 



OUR HOUSEHOLD INSECTS. 



By E. a. Butlee. 



HYMENOPTERA. 



THOUGH the order Hymenoptera is a very extensive 

 one, including, as it does, the bees, wasps, ants, 

 ichneumon flies, saw-flies, and gall-flies, it will not detain 

 us long, as only a very few of its members can legiti- 

 mately be claimed as household insects. Bees, saw-flies, 

 and gall-flies are so intimately associated with living 

 plants, that there is nothing to tempt them indoors, and 

 it is only amongst the parasitic ichneumon flies and their 

 allies, and the omnivorous ants and wasps, that we can 

 expect to meet with domestic examples. 



We will first take the ants. Of these insects we have 

 one species that is found exclusively in houses ; it is not 

 a truly British insect, but has been imported with mer- 

 chandise ; it does not seem to have been noticed here 

 before the year 1828, nevertheless it has completely 

 established itself, and, having found supplies plentiful, 

 and the climate of our houses congenial to its taste, it 

 will no doubt remain with us. At different times it has 

 been known to English entomologists under a variety of 

 names. In the latest systematic work on this particular 

 group of insects, the "British Heterogyna and Fossorial 

 Hymenoptera " of Mr. Edward Saunders, it is called 

 Monomoriuiii Pharaonis, but it was formerly known a.'> 

 Myrmica molesta and Diplorkoptrum molestum. 



Ants, as is well-known, are what are called social 

 insects, that is, they form large communities, which arc 

 something more than mere collections of many individual.s 

 of the same species living in close proximity to one 

 another (in which case they would be called gregarious, 

 but not social) ; they form well-organised societies, the 

 members of which share a common dwelling, and con 

 tribute to the common well-being by their united exer- 

 tions in erecting or excavating the abode, in providing 

 the common stock of food, and in rearing the young. 

 Insects which manifest this social instinct exhibit the 

 further peculiarity that the species is constituted not < f 

 two, but of three, distinct factors, which are frequently 

 called males, females, and neuters, though the last- 

 mentioned are more suitably denominated workers. As 

 far as British insects are concerned, the only truly social 

 species are ants, certain wasps, the humble bees, and the 

 hive bee, and it is only in these that the three so-called 

 sexes fire found. There is nothing comparable to the 

 worker in any other British insects, whether Hymenop- 

 terous or otherwise. In the highest development of the 

 social community, such as is met with in the hive-bee, 

 the males and females are simply concerned with the 

 propagation of the species, whilst the various labours f f 

 the community are performed by the workers, who are 

 themselves incapable of reproducing their kind, and nre 

 by some supposed to be a kind of ;iliii( i\ i feiiK,len. 



Now in the ants, the males and friii:il. ^ ai,., [ i'iiii:ii '_v 

 at any rate, winged, but the workers mit :il\\a_\s w iu-l, --; 

 moreover, the males and workers -.wc usually smaller tliaii 

 the females, sometimes very much so, and the work* rs 

 are usually also smaller even than the males. The males 

 and females appear in the late summer or autumn, and 

 the former perish after pairing, so that their period of 

 perfect existence is a very short one. The females, 

 previous to undertaking the duties of maternity, lose 

 their wings, which either drop off spontaneously, or are 

 torn off by the workers. Winged ants, therefore, arc 

 only to be seen at certain seasons of the year, and the 

 majority of the wingless creatures that we commonly 



