liAJRDWICKE'S SCIENCE-GOSSIP. 



15 



at great lengtli upon the habits of the various ob- 

 lects it describes. This is done in that pleasant 

 style which marks all Mr. Wood's books, and 

 yet affords us sufficient evidence that the author lias 

 been a careful and diligent obseiTcr of the habits 

 he describes. We quote the following remarks on 

 the Aphides as an example of the general treat- 

 ment : — 



"The Aphides form the food of very many in- 

 sects. The larvae of the Ladybirds feed entirely 

 upon them, and so do those of the Lace-wing flies. 

 They are also eaten by the larvoc of the swift and ac- 

 tive Syrphida. Several Hymenoptera provision their 

 nests with them, and others of the parasitic kind, 

 such as the Chalcidicaj, Proetotrupidse, Cynipida', 

 and Ichneumonidse. As to these last insects, the 

 way in which they operate on the aphis is very re- 

 markable. As may be inferred, from the size of the 

 aphides on which they are parasitic, they are of 

 very small dimensions ; and one of these tiny crea- 

 tures, when standing on the back of an aphis which 

 it is about to wound, looks much like a rook 

 perched on a sheep's back. 



" When the fatal egg has been introduced under 

 the skin of the aphis, the wounded insect, like the 

 stricken hart, separates itself from its fellows, and 

 passes to the under side of a leaf, and there fixes 

 itself. Its body soon begins to swell, and at last 

 becomes quite globular and horny, the change being 

 caused by the death of t'le aphis and the rapid 

 growth of the parasite within it. The Ichneumon 

 passes rapidly through its changes, and in a short 

 time assumes the perfect form, always with its head 

 near the tail of its victim, pushes off the last two or 

 three segments of the dead aphis, and makes its 

 escape into the world. The dead and empty skins 

 of such hapless aphides may be found plentifully 

 towards the end of summer, sticking firmly to the 

 leaf, and showing the round aperture through which 

 the destroying parasite has crept. Sometimes there 

 is a sort of contest between the aphis and the Ich- 

 neumon-fly, the former, however, having no more 

 chance against its tiny foe than has a rabbit against 

 a weasel. If the aphis have its beak deeply plunged 

 into the bark, the Ichneumon-fly has an easy task, 

 for the aphis can do nothing but kick and struggle 

 while anchored to the spot by its proboscis, and all 

 the Ichneumon-fly has to do is to make its deadly 

 lunge. But if the aphis be wandering about the 

 plant, the Ichneumon-fly has to walk about with it, 

 and try first one side and then the other, until she 

 can find an opportunity of depositing her egg." 



We give the following as a specimen of the 

 general character of the woodcuts. 



In the figure of tiie caterpillar of the Brimstone- 

 moth the reader cannot fail to see an example of 

 what has been well termed mimicry ; for nothing 

 could better represent the fragment of a twig of 

 white-thorn than the stretched-out condition of the 



caterpillar. The thorn-like prominences on its back 

 still further assist in the illusion. 



In conclusion, we should add that there are some 

 valuable notes in the book to the young dissector 

 and entomologist, and hints respecting nomencla- 

 ture, arrangement of specimens, &c. 



THE DRAGON-FLY. 



TTAVING in July last procured from a pond in 

 ^-^ the neighbourhood of Canterbury some pui a; 

 of the Dragon-fly, and carefully watched the full 

 development of the insect in my aquarium, I was so 

 delighted at the beautiful sight, that I have endea- 

 voured to give a descriptiou of it to the readers of 

 SciEXCE-GossiP. After witnessing the metamor- 

 phosis of three of them, I happened to read Ihe 

 account given in Science-Gossip by P. Pollock, of 

 his observations in Nov. ISGS (p. 245), and have 

 witnessed most of the things there described. He 

 remarks "that if the readers of Science-Gossip 

 eouldi be induced to watch, and be fortunate 

 enough to witness the change of the pupa into the 

 perfect Dragon-fly, they would be inclined to admit 

 that few sights in nature are more wonderful." 



No one for the first time witnessing the metamor- 

 phosis would (without being previously informed) 

 for a moment think that the position of the insect 

 was the natural one. They would most likely come 

 to the conclusion I did, that it must fall and be 

 injured, or killed. Under that impression I placed 

 a sheet of paper beneath its head, to prevent such a 

 mishap ; but the moment the paper touched the 

 head, the insect showed, by a peculiar movement, 

 that it was annoyed, and endeavoured to avoid 

 coming into contact with it. I soon found that 

 the seemingly unnatural and helpless position was 

 the proper one. 



It is amusing to observe the care the pupge ma- 

 nifest in getting into a position where nothing 

 can be in the way to obstruct their development. 

 One in particular came up out of the water, and 

 slowly climbed to the top of a reed I had placed in 

 it. To keep it perpendicular, I had inserted a piece 

 of wire about two inches from the top. This wire 

 was in its way, and its lowly retraced its steps 

 until it'arrived below it.'^ It then placed itself \a. the 

 usual position, and commenced lashing the body to 

 and fro, at the same time violently jerking it, evi- 

 dently to obtain a firm hold with its foot-cla\\-s on 

 the reed, preparative to the change about to take 

 place. When properly fixed, it became quite station- 

 ary for some time, and then a small opening became 

 perceptible in the middle of the upper part of the 

 thorax, and, gradually enlarging, the head of the fly 

 was drawn slowly out and thrown backward until 

 the head and thorax were clear of the pupa-case. 

 When it had reached this position it remained quiet. 



