INS 



Of the former, the highest place must be accorded 

 to those social insects which build nests of the most 

 beautiful construction, serving not only for the educa- 

 tion of their young (which are produced from eggs 

 placed in separate cells), but also for the habitation 

 of the entire community at large. We must refer to 

 our articles upon the BEE (Hive-Bee), HUMBLE BEE, 

 HORNET, WASPS, ANTS, and FORMICID/E, WHITE 

 ANTS, TERMITID^:, &c., for many details which it 

 would be useless to repeat. We are next to notice the 

 sand-wasps, and many solitary species of wild bees and 

 wasps, which construct their nests with great labour in 

 the sand or in rotten wood, forming a succession of 

 cells generally of an oval or rounded form, in which 

 they deposit a supply of food either of pollen, paste, 

 or other insects, sufficient for the nourishment of the 

 larva when hatched from the egg, which is placed in 

 the cell with this supply. We have already given 

 instances of this mode of proceeding in the "articles 

 CERCERIS, FOSSORES, CERATINA, HALICTUS, &c. 

 Here also may be ranked the dung-rolling and dung- 

 boring beetles, whose history we have given under the 

 articles GEOTRUPES and GYMNOPLEURUS, as well as 

 the burying-beetles (Necrophagm), whose exploits in 

 burying small dead animals, in which they deposit 

 their eggs, are not less indicative of a high degree of 

 instinctive powers. The Cicada likewise, as well as 

 the saw-flies, may also here be noticed, since the 

 care with which the parent constructs a burrow in 

 the stems of plants, for the reception of her eggs, by 

 means of a most admirably constructed apparatus, is 

 equally remarkable, although the larva, as soon as 

 hatched, is compelled to seek elsewhere for its food, 

 namely, the leaves on the adjoining twigs. But the 

 instinct which is exhibited in the selection of appro- 

 priate situations for the eggs, and where the larva, 

 when hatched, will find a supply of food, without the 

 same being laid up in store by the parent fly, is found 

 to be possessed by the greatest number of insects. 

 Many species of Iarva3 will feed only upon one parti- 

 cular species of plant ; and the parent fly, in its per- 

 fect state, takes no other food than a little honey from 

 every flower which may be in bloom at the time ; still 

 it is only upon that particular plant which suits the 

 taste of her progeny that she deposits her eggs. Here 

 are to be ranked many of the tribes of lepidopterous 

 insects (Butterflies and Moths). Many species of 

 moths, as well as beetles, reside in the larva state 

 under the bark of trees ; the females, therefore, by 

 means of a long and jointed ovipositor, are enabled to 

 place their eggs at the bottom of the crevices in the 

 external bark. In like manner, the carrion flies de- 

 posit their eggs upon carrion ; the flesh-flies upon 

 flesh ; the flies whose larvae feed upon plant-lice, in the 

 midst of the plant-lice ; and some species of these 

 flies (Hemerobnis) render the security of their young 

 doubly secure, by placing their eggs out of danger at 

 the extremity of long and slender foot-stalks (fig. 9). 

 In like manner, the boat of eggs formed by the gnat 

 (see our article CULICID^E), and the egg-pouch of the 

 Hydrous, are alike deserving of notice. But it is 

 amongst the parasitic insects that this species of in- 

 stinct appears most fully developed. Of this we have 

 already given numerous instances in our articles upon 

 the CUCKOO-BEES, OHRYSIDID^E, CHALCIDID^E, and 

 especially ICHNEUMONID.S ; whilst the proceedings 

 of the bot-flies, and the instinct whereby, as in the 

 Gasterophitus equi, a particular spot upon the body 

 of an animal is selected for the reception of the egg, 



NAT. H IS T._ VOL. II. 



E C T. 833 



is most remarkable. It would, however, be an almost 

 endless task to detail the various modes adopted by 

 insects in order to deposit their eggs in such situations 

 that their progeny may be sure of meeting with an 

 ample supple of food. 



If the instinct exhibited by the parent fly be worthy 

 of observation, the number of eggs which she de- 

 posits is not less interesting. Thus the queen bee 

 produces from 40,000 to 50,000 eggs in the course ot 

 a year, and supposing a swarm to contain 32,256 

 individuals, and three swarms to take place in the 

 season, the population of a hive would in a single 

 year amount to nearly 100,000 bees; and the Aley- 

 rodes proletella, a little homopterous insect, may give 

 birth in a year to more than 200,000 young. A 

 species of moth, according to Lyonnet, produces in 

 the third generation more than a million of young; 

 and the Aphis, observed by Reaumur and Bonnet, 

 produced at the fifth generation 5,904,900,000 indi- 

 viduals, and there may be not less than twenty 

 generations in the course of a year. The female 

 white ant, whose enormously distended body causes 

 her to exceed her companions many hundred times 

 in size, deposits sixty eggs in a minute, which is at 

 the rate of 211,449,600 in the course of a year. 

 Other insects are, however, less prolific. The silk- 

 worm produces only from 400 to 500 eggs, the 

 caddice flies less than 100; the burying beetles about 

 thirty, and the horsefly (Hippobosca equina) can only 

 be said to deposit a single egg. 



The eggs of insects are generally of an oval form 

 (fig. 1, oval-spotted egg of the fox-moth), the outer 

 covering being sufficiently rigid to resist ordinary 

 external impressions ; others are, however, soft and 

 pliant. In some species they are globose, as in many 

 lepidoptera (fig. 2, globular-banded egg of the 

 vapourer-moth) ; or conical, as in the large white 

 cabbage butterfly (fig. 3) ; cylindrical, pear-shaped, 

 barrel-shaped, &c. They are for the most part 

 smooth ; but many are very beautiful, ornamented 

 with symmetrical ridges (figs. 3 and 4, egg of the 

 tortoise-shell butterfly), canals, dots, &c., giving them 

 as Reaumur observed, the appearance of embossed 

 buttons. There are numerous other varieties in the 

 form of eggs, and some are furnished with appendages 

 for peculiar purposes. Thus the egg of the dung-fly 

 (Scatophaga putris, fig. 5) has two oblique props at 

 one end to prevent it sinking too deep in the matter 

 upon which it is deposited ; whilst those of the water 

 scorpion (Nepa cincrca, fig. 10) are furnished with a 

 coronet of spines forming a receptacle for the egg, 

 which is deposited immediately afterwards. 



The colour of insects' eggs varies very consider- 

 ably, although white, yellow, and green are the more 

 prevalent tints ; orange, red, brown, and black, with all 

 the intermediate shades, are to be found, as well as 

 blue ; and others are banded with pale circles, and 

 that of the pine lappet moths is blue with three brown 

 zones. The colours of eggs are, however, subject to 

 change as the inclosed larva approaches the period of 

 its escape, this being owing chiefly to the change ot 

 GGG 



