HARDWICKE'S SCIENCE-GOSSIP. 



moisture is usually followed by conditions that are 

 diametrically opposed to those that prevailed while 

 the sirocco was blowing. 



The frequent and rapid changes that the stone thus 

 undergoes, causes an abnormal expansion and con- 

 traction of the superficial molecules, and so tends to 

 make the surfaces readily disintegrate and peel off in 

 large flakes. 



The work of erosion is greatly assisted also by the 

 crystallization of the salt contained in the moisture 

 that this wind takes up in its passage across the 

 Mediterranean. 



This moisture renders the stone surfaces highly 

 saliferous. Under the influence of the heat of a 

 semitropical sun, the moisture passes off, and the 

 salt crystallizes and pushes out the superficial particles 

 of the limestone, thus facilitating the paring down 

 process which so rapidly wastes the rocks, and causes 

 them to break up. 



NOTES AND OBSERVATIONS ON 

 CHELONIA CAJA. 



By H. DURRANT. 



THE following paper consists merely of extracts 

 from my diary and notes made at the time of 

 observation and experiment. I do not claim any 

 great originality for them, as most of the experiments 

 were made to prove statements made by more dis- 

 tinguished workers than I, but still, perhaps they 

 will be found interesting and probably new to some 

 readers. The larva which I kept for observation was 

 one of the commonest I could procure, both as 

 regards itself and its food. The cages were made 

 of fine gauze with glass fronts, which are easily and 

 cheaply constructed, filled to the depth of about two 

 inches with fine mould, in the middle of which was 

 fixed a small glass, about four inches high, half-filled 

 with water. Into this the branches of food-plants were 

 put. For isolation I obtained some ordinary card- 

 board starch-boxes, cut out an oblong hole from the 

 lid and fixed on the under surface with " Kay's 

 coaguline," a quarter-plate negative glass (cleaned of 

 course) ; a number of holes were then pricked in all 

 over the box, for the free admittance of the vital 

 principle, air. 



On April 24th, I went out in quest of the cater- 

 pillars of the tiger-moth (Arctia caja), and after 

 traversing several miles and getting splendidly 

 nettled, I brought home about thirty, principally 

 taken from the nettle {Lamium album) and the dock. 

 I also took several from a small patch of moschatel 

 (Adoxa moschatdlina), which was in flower at the 

 time. I have never met with any lepidopterous 

 larvae on this plant before, nor do I remember 

 having heard of anyone else finding larva; on it, but 

 on this point I should like to hear other correspon- 

 dents' experiences. At first I thought I had several 



different species, as in some the* hair was extremely 

 short and in small tufts, but to make up for this short- 

 coming, as it were, the spiracles were very visible. 

 In others the hair was very long and of a silky ap- 

 pearance. I placed them all together in a cage and 

 left them withJ some food. Next morning when I 

 came to examine them, I found scarcely any with the 

 short tussocks of hair and large spiracles, but the 

 cast-off skins were plentifully strewed about the sides 

 of the cage. Later in the day I saw several more 

 change their skin. Just before changing it they 

 invariably attached themselves to the side of the cage 

 by a silken thread, and the empty skin would remain 

 there after the larva had escaped and assumed its- 

 new coat. After they have done so they look wet 

 and miserable, and their hair seems matted together 

 as it would be if they had been dipped in water. But 

 they soon dry (.themselves, when Jhey appear very 

 handsome in their silky coat. In about a week they 

 had all been through the operation — painful it would 

 seem — of changing their skin. During the earlier 

 stages of their voracious life, and just before changing, 

 they would scarcely eat anything, but when they 

 reached what 1 'may term the long-hair stage, they 

 ate ravenously, comfrew, nettle, dock, horse-raddish, 

 Mentha rotundifolium, and in fact nearly anything I 

 could supply them with. I fed them sometimes twice 

 and three times a day, such was their insatiable 

 appetite. Burmeister mentions the fact that beetles- 

 and their larvae never consume the leaf from the 

 margin, like the caterpillars of Lepidoptera, but bite 

 a hole in the centre, round which they feed, thus dis- 

 tinguishing the destroyer merely by the appearance 

 of the leaf. This certainly must be a fallacy. 

 Lepidopterous larva; not only feed from the edge of 

 the leaf, but as often as not will commence in the 

 middle, though generally a'rom beneath. This must 

 be a common occurrence to those who have kept larva? 

 in confinement. As to the beetles they certainly do 

 feed from the middle of the leaf, but they are fre- 

 quently to be seen feeding from the edge. Go out 

 some summer evening with a lantern and examine 

 the leaves of any common plant, and you will be able 

 to verify this statement. So that the appearance of 

 the leaves is in no way calculated to apprise the stu- 

 dent of their respective invaders. Another item of im- 

 portance is the following. Most entomologists agree 

 that there are few lepidopterous larvae, if any, which 

 prey upon each other. But while I kept Chelonia I 

 found that when a larva had just pupated, and while 

 the external skin was soft and moist, the larvae would 

 gather round it, bite pieces out of it, and apparently 

 eat them, leaving afterwards a dry, deformed, 

 shrivelled up shell. This occurred while the cage 

 contained plenty of food, so that hunger cannot be 

 thrust in as an excuse. Not only this larva, but a 

 number of others which I have kept at various times, 

 particularly the common tumip-moth, have exhibited 

 the same propensities. If, however, the skin of the 



