HARDWICKE'S SCIENCE-GOSSIP. 



73 



GRAPHIC MICROSCOPY. 



By E. T. D, 



No. XVI. — Eggs of Vapourer Moth. 



4^{f?^teli^ IIE ' outer "shell" 

 (if it may be so 

 called), of the eggs 

 of the majority of 

 insects is composed 

 of a chitinous 

 membrane, of such 

 protective tough- 

 ness, that the eggs 

 are frequently 

 found in the crops 

 of insectivorous 

 birds, mixed with 

 digested portions 

 of food, so intact 

 and unaltered in 

 form, colour, and 

 integrity, as pos- 

 sibly to be found 

 to retain even their 

 vitality. In the article accompanying the plate of the 

 egg of the house-fly in the October 1884 number of 

 this journal, on page 218, an authentic case is referred 

 to, of the eggs of the vapourer moth {Orgyia antiqua) 

 having been found in large numbers in the intestines 

 of a cuckoo, which was captured last August in the 

 garden of the old Charterhouse School, London, 

 and a detailed account of the circumstances pub- 

 lished in the "Field" newspaper on the 30th of 

 the same month. The present illustration shows a 

 group of these eggs, after having been extracted, 

 washed, and carefully dried; although the experi- 

 ment was not tried, it is possible they might have 

 been hatched. 



The regularity of the various forms of the eggs of 

 insects, added to exceptional appearances of colour, 

 markings, and even sculptures, render them peculiarly 

 attractive as microscopic objects. As a distinct subject 

 of interest, they offer great diversity and beauty — 

 unlike the eggs of birds, exhibiting external appliances, 

 strange structural appendages, fringes of extreme 

 delicacy, eccentric forms and curvatures, with lids, 

 No. 244. — April 1885. 



and caps of various devices to aid the emission of 

 the larva. 



It is not unworthy of note, that sculptured surfaces 

 of rare beauty, raised nodules, pitted depressions, 

 surrounded with ridges arranged with geometrical 

 precision, radiating from the base to the apex, as 

 found in the eggs of some insects, are peculiarities 

 frequently seen in minute, and isolated germ life, in 

 unicellular plants, the cells of desmids, diatoms, 

 minute seeds, spores, and particularly in pollen 

 granules where external appearances take the most 

 singular and elegant forms. 



The collector of the eggs of insects must be guided, 

 in his explorations, by the habit of the parent. The 

 suitable deposition of the egg, and its future develop- 

 ment, depend on the supply and position of the food ; 

 it would be impossible to conceive an organism in a 

 more helpless condition than a larva just emerged, 

 unless it found itself surrounded by, or within reach 

 of, abundant nutriment ; the eggs of all leaf-eating 

 caterpillars are consequently deposited on the 

 branches, and in the interstices of the trees themselves, 

 or in close proximity. Particular trees or plants, 

 probably with some regard to locality and aspect, are 

 selected by different species. In some cases the parent 

 collects and stores the future food, depositing an egg in 

 a cell, and packing it with just the amount required by 

 the larva, anticipating a supply in proportion to the 

 size of the cell which invariably is a sufficient, and 

 an exact, quantity. Many of the vegetable-feeding 

 beetles maintain the preservation of the future progeny 

 by rolling up balls of food, in which is enveloped an 

 egg — a case where the individual is evidently of less 

 importance than the perpetuation of the species, the 

 chances of survival being enhanced by the separate 

 isolation of the egg. It is engagingly interesting to 

 consider the powerful impulses which induce such 

 actions ; involving favourable positions, selection of her- 

 bage, and often temperature and moisture, as affecting 

 the putrefaction or fermentation of organic substance 

 in which the young maggots may revel, an impulse 

 without doubt emanating from maternal presentiment 



