ON MICROSCOPIC DISCOVERY. 



611 



which the magnified drawing was made. 

 As it approaches maturity, it casts its skin 

 several times, from each of which it escapes 

 by a rent formed down the back." 



" In this larva the air is supplied for res- 

 piration by proper orifices situated at the tail ; 

 and the creature is obliged to ascend to the 

 surface of the water, and elevate its tail out 

 of it, at every inspiration. When the air thus 

 inhaled has become unfit for inspiration, it is 

 expelled at the same orifice, and a small 

 bubble may frequently be seen issuing from 

 the tail, and ascending in the water. On a 

 careful examination of the skin, which by the 

 bye affords an excellent object for the micro- 

 scope, there will not appear any spiraculse 

 along the sides, as in perfect insects." 



We have been compelled to abridge Mr 

 Pritchard's description from want of space, 

 and we have likewise made a few necessary 

 verbal alterations to connect it with our wood 

 engraving : in the Microscopic Illustrations, 

 the figure is exhibited in a most elaborately 

 executed coloured plate. 



The preceding instance has shown us the 

 voracious and tierce propensities of insects in 

 the larva state ; we now reverse the picture, 

 and discover the sufferings and inconveniences 

 to which they are themselves exposed. The 

 following are the curious observations of an 

 ingenious naturalist. " As I was observing," 

 says he, "one day some caterpillars which were 

 feeding voluptuously on a cabbage leaf, my 

 attention was attracted to a part of the plant, 

 about which a small ichneumon fly was buzz- 

 ing on its wing, as if deliberating where to 

 settle: 1 was surprised to see the herd of cater- 

 pillars, creatures of twenty times its size, en- 

 deavouring, in an uncouth manner, by various 

 contortions of the body, to get out of its way, 

 and more so whenever the fly poised on the 

 wing as if going to drop ; at length the crea- 

 ture made its choice, and seated itself on the 

 back of one of the largest and fairest of the 

 cluster : it was in vain the unhappy larva en- 

 deavoured to dislodge the enemy. If the 

 caterpillar had shown terror on the approach 

 of the fly, its anguish at intervals now seemed in- 

 tolerable, and I soon found that it was in con- 

 sequence of the strokes or wounds given by 

 the fly. At every wound the poor caterpillar 

 wreathed and twisted its whole frame, en- 

 deavouring to disengage itself, by shaking off 

 the enemy, sometimes aiming its mouth to- 

 wards the place ; but it was all in vain, its 

 little, but cruel, tormentor kept its place. 

 When it had inflicted thirty or forty of these 

 wounds, it took its flight with a visible triumph ; 

 in each of these wounds the fly had deposited 

 an egg. I took the caterpillar home with me 

 to observe the progress of the eggs which 

 were thus placed in its body, taking care to 



give it a fresh supply of leaves from time to 

 time, it recovered to all appearance in a few 

 hours from the wounds it had received, and 

 from that time, for the space of four or five 

 days, seemed to feed with its usual avidity. 

 The eggs were all hatched into small oblong 

 voracious worms, which fed from the moment 

 of their appearance on the flesh of the cater- 

 pillar, in whose body they were inclosed, and 

 seemingly without wounding the organs of 

 respiration or digestion ; and when they had 

 arrived at their full growth, they ate then- 

 way out of the sides of the larva, at the same 

 time destroying it. The caterpillar thus at 

 tacked by the larvae of the ichneumon fly never 

 escapes, its destruction is infallible ; but then 

 its life is not taken away at once ; the larva, 

 while it is feeding thereon, knows how to 

 spare the parts which are essential to its life, 

 because its own is at that time tied up in that 

 of the caterpillar. No butterfly is produced 

 from the caterpillar ; the worms that feed on 

 the wretched creature, are no sooner out ot 

 its body, than every one spins its own web, 

 and under this they pass the state of rest ne- 

 cessary to introduce them to their winged 

 form." 



We conclude our notices of larvae with an 

 extract from Burt's " Observations on the 

 Curiosities of Nature," which appeared in 

 Chambers' Edinburgh Journal. The details 

 here offered are very similar to those just 

 given ; there are, however, several new and 

 interesting facts connected with the present 

 instance, which justify the partial repetition. 



" The capada worm, or insect-fly carrier, 

 is produced, like the silk- worm, from the eggs 

 which its mother scatters every where, alter 

 she has undergone her metamorphosis into a 

 white butterfly. It begins to live at the end 

 of July, and at its birth is arrayed in a robe 

 of the most brilliant and variegated colours. 

 When on the point of undergoing its meta- 

 morphosis in August, it throws off this superb 

 livery, and puts on another of an admirable 

 sea-green hue. This fundamental col ur re- 

 flects all its various shades, according to the 

 different undulations of the animal, and the 

 different accidents of light ; but this new de- 

 coration announces the approach of a period 

 when it is doomed to undergo great tortures. 

 It is immediately assailed by a swarm of 

 ichneumon flies, one of which inserts itself into 

 each of the pores of its body, not an opening 

 being left unoccupied. All its struggles to 

 get free of its tormentors are in vain. These 

 flies, which are so small they can only be 

 studied by the microscope, drive their stinr 

 into the skin of their victim, over the wjd 

 extent of its back and sides. Afterwar^ggs 

 all at the same moment, they slip th&have 

 into the bottom of the wounds which 





