—— Origin and metamorphoses of insects. (Nature, 1873 [in book form, 1874], pp. 108, 66 Figs.)
Mayer, Paul. Ueber Ontogenie and Phylogenie der Insekten. (Jena. Zeitschr. Wissens., x, 1876, pp. 125–221, 4 Taf.)
Hyatt, A., and Arms, J. M. Insecta. (Bost. Soc. Nat. Hist. Guides for science-teaching, viii.) Boston, 1890, pp. 300, 13 Pls., 223 Figs.
c. Growth and increase in size of the larva
The rapidity of growth and enormous increase in size in early life is especially noticeable in caterpillars and other phytophagous larvæ. The latest observations are those of Trouvelot on Telea polyphemus. When this silkworm hatches, it weighs 1
20 of a grain.
When
| 10 days old it weighs | ½ a grain, or | 10 times the original weight. |
| 20 days old it weighs | 3 grains | 60 times the original weight. |
| 30 days old it weighs | 31 grains | 620 times the original weight. |
| 40 days old it weighs | 90 grains | 1800 times the original weight. |
| 56 days old it weighs | 207 grains | 4140 times the original weight. |
“When,” he says “a worm is 30 days old, it will have consumed about 90 grains of food; but when 56 days old, it is fully grown and has consumed not less than 120 oak leaves, weighing ¾ of a pound; besides this it has drank not less than ½ an ounce of water. So the food taken by a single silkworm in 56 days equals in weight 86,000 times the primitive weight of the worm. Of this about ¼ of a pound becomes excrementitious matter, 207 grains are assimilated, and over 5 ounces have evaporated.”[[94]]
Dandolo stated that the Asiatic silkworm (Bombyx mori) weighs on hatching not over 1
100 of a grain, but when fully grown about 95 grains. During this period, therefore, it has increased 9500 times its original weight, and has eaten 60,000 times its weight of food. Newport thought this estimate of the amount of food was a little too great. But comparing it with Trouvelot’s estimate for the American silkworm, which weighs when hatched five times as much, it would not appear to be so. Newport found that the larva of Sphinx ligustri at the moment of leaving the egg weighs about 1
80 of a grain, and when fully fed 125 grains, so that in the course of 32 days it increases about 9976 times its original weight. This proportion of increase is exceeded by the larva of Cossus ligniperda, which, boring in the trunks of trees, remains about three years in the larva state, and increases, according to Lyonet, to the amount of 72,000 times its first weight.
Newport adds that those larvæ in which the proportion of increase is the greatest, are usually those which remain longest in the pupa state, as in the silkworm. “Thus Redi observed in the maggots of the common flesh-flies a rate of increase amounting to about 200 times the original weight in 24 hours, but the proportion of increase in these larvæ does not at all approach that of the Sphinx and Cossus.” From his observations on the larva of one of the wild bees (Anthophora retusa) Newport believes that this is also the case with the Hymenoptera. The weight of the egg of this insect is about 1
150 of a grain, and the average of a full-grown larva 68
10 grains, so that its increase is about 1020 times its original weight; “which compared with that of the Sphinx of medium size, is but as 1 to 9¾, and to a Sphinx of maximum size only as 1 to a little more than 11.”