March 1,1897.] 



KNOWLEDGE. 



75 



inch and a quarter long. At first it examined the artificial 

 burrow, and evidently did not fancy living there with one 

 side transparent, so it deliberately descended to the bottom 

 and took up a mouthful of damp sand, which it plastered over 

 the glass. This act was repeated a number of times until 

 the larva had covered in a height of an inch and a half. 

 I removed the sand and larva from the glass, refilled and 

 renewed the hole at the side, and once more replaced the 

 larva ; and it once more, and many more times, plastered 

 the glass, until at last it resigned itself to circumstances 

 and became accustomed to my magnifier. 



I found that it used its mandibles for excavating. 

 Taking up a mouthful of sand, it turned its head up and 

 fixed the sand above until a small load had collected ; this 

 was rammed up by the head, as the larva crawled up the 

 hole, until the surface was reached, when the sand was 

 balanced on the mandibles and front of the head, which 

 was then jerked backwards with a sudden movement, and 

 the sand sent flying to a distance of ten or twelve inches. 

 When deepening its hole various impedimenta are met 

 with — tiny pebbles of quartz, each of which is brought up 

 between the mandibles, balanced, and shot away, and 

 frequently as not rolls down the burrow of a neigh- 

 bouring larva, which brings it up to the top, and in its 

 turn throws it away from its door. When all such impedi- 

 menta had been removed, and the hole nicely smoothed, 

 the larva would ascend to the top, and, raising its head 

 above the surface, commence to bite mouthfuls of sand 

 from around the edge until a rough enlargement had been 

 made ; then, raising its head well above, it hammered with 

 its swollen chin into this until a perfectly smooth concavity 

 had been formed all round, the exact curve of the chin. 

 It was astonishing with what force the blows were given. 

 As soon as the pitfall was completed the larva rested 

 from its labours by placing the head and first semicircular 

 thoracic plate almost level with the top of the hole, in 

 which the plate and head exactly fitted, the open and 

 turned-up mandibles resting in the curved sides of the pit- 

 fall — ready to close at a moment's notice should any insect 

 chance to stray across, when it and the larva both 

 disappeared to the bottom. I could not ascertain by what 

 means the larva was supported until it had become 

 accustomed to the hole at the side of the glass jar. Then 



I discovered that the 

 larva was drawn up 

 into the most extra- 

 ordinary position, the 

 thoracic segment 

 "close-hauled" under 

 the chin, beuding 

 round at the fourth 

 abdominal one in a 

 backward curve, until 

 the large prominence 

 on the fifth was 

 brought under and 

 pressed against the 

 thorax, the two vertical 

 spines at the top being 

 driven into the side of 

 the burrow. The anal 

 segment curled round 

 to the opposite side, 

 into which the spines 

 were driven, so holding 

 the larva up most 

 securely. Thus, the 

 body, when seen sideways, formed a perfect zigzag or 

 (letter S (Fig. 3). 



iS 







Noticing that the larvfe frequently jerked up their heads 

 without any apparent reason, I placed a box on my 

 window-sill, and when there I observed a number of small 

 spots of a dirty fluid appear on the window two feet above 

 the box. I then placed a piece of paper at that distance 

 above, and found the spots appear on the under- 

 side, proving that the larvse performed the trick, as I 



Fia. 4. — Larva : Act of seizinj; its Pr 



3. — Larvi 



I'ej'. 



imagined, to create a disturbance among the various flies 

 moving about. Thinking that they were able to seize their 

 prey before it crossed the pitfall, 1 placed flies near, and, 

 when within half an inch, they vanished with such rapidity 

 that I could not at first detect the movement ; but on holding 

 a fly between the pliers I brought it within a quarter of an 

 inch of the front of the head, and though the larva evidently 

 saw it, it did not attempt to seize it until it had quietly 

 lowered itself down the hole, reappearing in a few moments 

 with the back of the head turned towards the fly, which 

 was instantly seized by the larva springing out and striking 

 the fly from above ; the movement reversed, when larva 

 and fly disappeared in the dark abyss. I gradually increased 

 the distance so that I could entice the larva to repeat its 

 attempt several times ; this was done until I found that a 

 fly could be reached when placed five-eighths of an inch 

 fi-om the hole, the larva always throwing itself backward. 

 When making these long shots, as I term them, from the 

 hole, the larva would sometimes retain its hold on the fly 

 while I did the same, so that 1 was enabled to see that it 

 was in some way held in its burrow. By a careful arrange- 

 ment of silken cords attached to the dead fly, I was able 

 to draw it near whilst I examined the movements of the 

 larva from the light side of the glass. Waiting until one 

 was quietly resting in the zigzag position, I placed my eye to 

 the fixed magnifier, drew the cord, bringing the fly towards 

 the hole, and from a sUght movement I concluded that the 

 larva had seen it. An eighth of an inch nearer and out 

 sprang the tiger from its den, the body from the first 

 to the eighth segment being arched backwards above the 

 level of the vertical hole. The fly was seized and held 

 fast by the tiger and my cord. A regular " tug of war " 

 commenced, during which I had time to see that the larva 

 was securely anchored in its burrow by the long dorsal 

 pair of spines on the fifth abdominal (ninth from the head) 

 segment being driven deep into the side of the burrow 

 just below the pitfall, and to still further strengthen its 

 hold the anal spines were driven into the opposite side. 



Thus securely anchored, the larva could defy any attempt 

 made by its struggling prey to drag it from its lair {see 

 Fig. 4). As soon as I released my hold on the silk cord, all 



