July 1, 1889] 



KNOWLEDGE ♦ 



181 



circular segment bebind just blocking up the entrance, and 

 maintains itself in tbis vertical position by means of its legs 

 and dorsal liooks. Here it remains in ambusli, witb jaws 

 ■wide open, till some unwary insect comes within reach, when 

 the head is violently jerked backwards and the prey seized 

 by those relentle.-s jaws with a tenacity of grip that rendtrs 

 futile all eflbrls at escape. The grub then hurries to the 

 bottom of its den, dragging its prey with it ; here it crouches, 

 bending its body somewhat in the form of a Z, and devours 

 its victim at lei>ure. As might be expected of an insect 

 that trusts so much to chance for a meal, it is not at all 

 fastidious, but will eat any living thing that comes in its 

 way, not disdaining even its own species. 



The exact length of time spent by the insect in this con- 

 dition is diliicult to estimate, and probably depends to some 

 extent upon the abundance or scaieity of food. Larv.-e, as 

 well as perfect insects, may be found during a great part of 

 the 3 ear, and the exact periods of its changes cannot be 

 stated with any cartaint}-. Like all other beetles, it becomes, 

 when full fed, a helpless pupa or chrysalis ; not a limbless 

 thing such as that of a butteifly or moth, but more lifelike, 

 inasmuch as the legs and other organs are apparent on the 

 outside, though of course covered with a skin which renders 

 them quite unusable. In this helpless condition it lies at 

 the bottom of its burrow till ready to make its final moult, 

 taking no food, but quietly etfecting beneath its skin all those 

 marvellous changes that are necessary to transform it from 

 an unadorned, fleshy, crawling grub, into a bard-cased, 

 brilliantly-coloured, fiying, and predaceous beetle. Before 

 becoming a chrysalis, it is said to guard against intrusion by 

 (losing the entrance of its burrow. When the bright spring 

 weather romes round, it issues from its subterranean 

 chamber in its perfect form, a sparkling, agile hunter, 

 destined never to return to its hermit cell, but to spend the 

 rest of its days ba'-king in the sunshine, making war upon 

 the other denizens of its ancestral bank, and laying the 

 foundations of future generations. 



PHOSPHATES AS FERTILISERS. 



]!y I). A. Louis, F.I.U., P.C.S. 



iroSPHOUUS in the free state is a highly 

 iuflamuiable and remarkably poisonous sub- 

 stance; it is familiar to every one as a mate- 

 rial used in the manufactuie of matches, and 

 ns a constituent of a paste for poisoning mice. 

 When phosphorus is ignited in the air it burns 

 with considerable briskness, evolving great 

 heat and clouds of smoke. The product of the burning is 

 a white substa'ico, which dissolves readily in water, and 

 has an intensely sour taste as well as other properties 

 characteristic of a strong acid ; it is, in fact, the substance 

 known as phosphoric acid. By mixing this acid with an 

 alkali or base, such as soda, potash, or lime, all the acid 

 properties and the sour tasto disappear, because the phos- 

 phoric acid and the base become intimately and firmly 

 attached to one another, forming a compound having neutral 

 properties and known as a " phosphate." In this form not 

 only is the phosjihorua non-poisonous, but it even becomes 

 an essential constituent of living matter, and neither 

 animals nor plants can thrive unless they receive a proper 

 supply of it. Phosphates must theretbro bo included in our 

 food. We either directly (as from broad and vegetables) or 

 indirectly (through meat or the flesh of animals feeding on 

 vegetation) obtain our supply of pho.sphatcs from the 

 vegetable kingdom ; therefore, in order to discover the 

 .source of our own phosphate supply, wo must learn which 



plants contain phosphates, where they get them from, and 

 how they get them. The existence of phosphates in plants 

 is easily demonstrated, for when a plant is burnt the phos- 

 phates remain in the ash, and numerous careful analyses of 

 plant ashes have enabled chemists to ascertain the average 

 amount present in different plants. The numbers repre- 

 senting the average quantity of phosphoric acid present in 

 some of our most useful crop plants are arranged in the 

 second column of the following table, and in the third 

 column are given the numbers representing the average 

 quantity of ash which remains when 100 lbs. of the various 

 plants are burnt ; whilst the data in the fourth column show 

 how much of this a.sh consists of phosphoric acid. In the 

 first column are placed the names of the materials to which 

 the various numbers relate. It is interesting to notice how 

 each plant collects a diBerent amount of phosphoric acid, 

 and disposes of most of it in such a way as to be of use to 

 succeeding generations of the plant. Thus the large.st pro- 

 portions of phosphoric acid are accumulated in the seeds ; 

 or when the roots store up nourishment, as in the case of 

 turnips and potatoes, the preponderating quantity of phos- 

 phoric acid is found in the roots, which if left in the ground 

 would serve as a store of food for the future development 

 of the plants. 



All these plants, and in fact all plants, obtain their 

 phosphoric acid from the soil, and insignificant as the 

 amounts appear in the above table, nevertheless, when the 

 total weight of crop is taken into consideration, the real 

 magnitude of these quantities soim becomes manifest. It 

 is found, for instance, that a crop of wheat yielding 30 

 bushels of grain per acre will take from the soil a quantity 

 of phosphoric acid which would be represented by a dress- 

 ing of over 1 10 lbs. per acre of a rich superphosphate 

 containing lT) lbs. of soluble phosphate in every 100 lbs. 

 In a similar manner a crop of barley yielding +0 bushels 

 per acre will remove phosphoric acid equivalent to a dress- 

 ing of nearly 140 lbs. per acre of this rich superphosphate, 

 whilst the phosphoric acid removed by a crop of 6 tons of 

 potatoes, or 17 tons of turnips, or L'2 tons of mangels per 

 acre, would bo lepresented respectively by dressings of IGl', 

 of more than 'llO, and above o50 lbs. per acre of the super- 

 phosphate. 



And the farmer has to produce at the present time such 

 crops as these, or even larger ones, in order to make things 

 pay. It must be remembered, too, that most of the phos- 

 phoric acid removed from the soil in these crops is irre- 

 trievably lost to it; for except when crops are used for 



