April 13, 1883.] 



KNOWLEDGE 



219 



What we call boiled meat, as a boiled leg of mutton or 

 round of beef, is an intermediate preparation. Tlie heat 

 is here communicated by wattr, and the juices partially 

 retained. 



Note.— A correspondoiit tells me that )ic has tried the metliixl of 

 cookiog egKS whicli 1 recoiiimciuk'J, and he states tliat liis eirfj" 

 " were not cooke<l at all." t'rom what I can Iciirn by his letter, ho 

 omitted to attend to the quantity of water I named, viz., about a 

 pint. 



As this is of essential importance, I should perhaps have stateil 

 it with some emphasis. More than a pint should be used nithrr 

 than less, as upon the quantity of water depends the retention of 

 the heat. If the quantity of water is smaller, it should be kept 

 boiling about half-a-minute before setting aside. 



PLEASANT HODRS WITH 

 MICROSCOPE. 



THE 



By Henry J. Slack, F.G.S., F.RM.S. 



EVERYONE who has a greenhouse, and many who have 

 only a few flowers in a window, are sure at this time 

 of the year to be supplied with objects of great interest to 

 the naturalist, though a sad plague to the gardener. Plant- 

 lice, thrips, and so called red spiders are sure to swarm as 

 the warm weather comes, iinless active warfare has been, 

 and continues to be, waged against them. It is with the 

 plant-lice or aphides that we are now concerned. A vast 

 number of plants — from humble weeds to great forest 

 trees — are infested with different kinds of sucking insects 

 belonging to this group, and near them are the tribes of 

 mealy-bugs, scale -bugs, mussel -bugs, Ac, that injure 

 orchards and wall-trained fruit-trees. 



A few days since, a large trumpet - lily (liicliardia 

 ..Elhiopica) showed a few aphides in little groups on its 

 stalks and on some leaves. Day by day the groups in- 

 creased at a rapid rate, and large colonies were soon formed. 

 The process was allowed to go on for a little while for the 

 sake of watching it. The first things noticeable on ex- 

 amining a group were that they differed greatly in size, and 

 that the biggest were marked with black on their backs, 

 the rest of their bodies being green. The smaller ones 

 were of paler, yellowish green. 



It is always best to begin with examining oVjjects whole, 

 and studying what is obvious before proceeding to details. 

 Such small soft insects as plant-lice should be lifted care- 

 fully with a needle stuck in a wooden handle, or with a 

 long, stout bristle from a broom. Those intended for im- 

 mediate examination may be collected on a plate of glass, 

 or on a card, and others, if the supply is not close at hand, 

 should be carefully placed in a little bottle,'such as Homoeo- 

 pathic chemists use, or in a goose-quill stopped with a little 

 plug of cotton wool. 



A small group of big and little ones may Ije seen alto- 

 gether with a power of from 30 to 50. Then two of the 

 largest should be selected, and placed on a glass slide that 

 has been touched with a very little gum-water. One 

 should be laid on her back, and the other on the under 

 side. The specimens caught on the trumpet-lily correspond 

 in size and markings with Siphonophora circumjlexa 

 of Buckton's great work on British Aphides. They 

 are wingless, viviparous females, and, as we shall 

 see, quite ready to produce a numerous family. Mr. 

 Buckton gives the size of full-grown ones as 0070 x 0030 

 inches. Their shape in an oblong oval, gradually swelling 

 out in a graceful curve from the head to the lower third 

 of the abdomen, and then getting narrower and ending 



bluntly. The back of the adult is ornamented with a long 

 horse-shoe row of irregular black spots, the rounded curve 

 being near the end of the abdomen, and the two open parts 

 beginning just below the head. The contrast of black and 

 green has a very pretty effect, which the smaller and 

 younger specimens do not show. It is a coming-of-age de- 

 coration. Six legs are noticeable, ending in small, hooked feet. 

 The most striking thing in the one lying on its back is the 

 proboscis or long snout, which folds down over the thorax, 

 and reaches to near the third pair of legs in the adult, and 

 lower still in the undevelopeil young. This kind of mouth 

 belongs to some other groups besides the Aphides, and 

 differs widely from the biting mouths of beetles, the more- 

 complex sucking ones of butterflies and moths, and from- 

 the licking ones of bees. It consists of a sort of tube in 

 three joints, the longest near the head, and two smaller ones 

 at the tip. A grooved line is seen with a low power, and. 

 most likely in one specimen or another three very slender, 

 flexible, and sharp-pointed lancets will either be projected 

 from the tip or elevated upwards out of the groove. The 

 stout rostum or proboscis is regarded as an extension of 

 the labruin, or under-lip, of ordinary insects, and the three 

 flne piercing tools as representing the mandibles and 

 maxillae of a typical insect. Mr. Buckton says the second 

 joint of the proboscis appears to be perforated, not 

 channelled, like the others, but this is difficult to make out 

 From the small size of the whole apparatus, and the 

 extreme fineness of the setie, or piercing bristles, it is not 

 at all easy to take them out with a needle, but they often 

 come out when the creature is immersed in a fluid. Before 

 making any dissections, the easily-visible organs should 

 be well studied in the living animal. The plan mentioned, 

 of keeping a couple quiet with a little gum, does for a 

 beginning, but a better one will be described in the 

 next paper. Besides the proboscis, the eyes of the creature 

 will appear striking. They are of a flne red tint. Each 

 large compound eye has round lenses and little knob of 

 eyes, also compound, stuck on to it at one corner. The 

 lenses of these supplementary eyes are rather larger than 

 the others, and no one knows what use they are. The head is 

 short, and the first segment of the thorax looks at first sight 

 scarcely separated from it. The antenna; are very long. They 

 spring fromastout projection, and are six jointed (seven is the 

 full number). The first two joints short, followed by longer 

 ones. The last one is long, looking, when highly magnified, 

 like four or five dozen miniature garden-pots, one inside 

 the other, the end ones being a little longer, and the whole 

 finishing with a fine bristle. Besides tapering, the last 

 joint makes a sudden diminution of diameter at about 

 one third from its commencement. The segments become 

 abruptly smaller, the last of the larger ones projecting on 

 one side, the first of the smaller ones being out of centre 

 and fixed to the other side. This gives a notched appear- 

 ance. Looking to the tail-end of the creature, two remark- 

 able organs stick out from the thickest part of the abdomen. 

 They are shaped like the funnels of a steamboat, cylindrical 

 tubes turning over at the top, and contain some oUy-look- 

 ing globules. They are the cornicles, sipuncles, or nec- 

 taries, and secrete a sweet fluid. The aphides which certain 

 ants keep as we do cows, give out this fluid when their 

 proprietors stroke them in a sort of milking process. The 

 tail of the species before us is seen, when protruded, to be 

 like a short stout club covered with tubercles. 



The inside of the aphid is crowded with oily globules, 

 and most likely one, or perhaps several, unborn infants can 

 be discerned. Their red eye spots show their whereabouts, 

 and if a few of the adults are kept in a warm room in a 

 glass cell, the birth process is sure to be seen by fretjuent 

 watching. The little things make their entrance into life 



