SCIENCE. 



525 



RETARDED DEVELOPMENT IN INSECTS* 

 By C. V. Rilev, Washington, D. C. 



In this paper the author records several interesting 

 cases of retarded development in insects, whether as sum- 

 mer coma or dormancy of a certain portion of a given 

 brood of caterpillars, the belated issues of certain^mag- 

 ines from the pupa, or the deferred hatching of eggs. 

 One of the most remarkable cases of this last to which 

 he calls attention, is the hatching this year of the eggs of 

 the Rocky Mountain Locust, or Western Grasshopper 

 {Caloptemus spretus), that were laid in 1876, around the 

 Agricultural College at Manhattan, Kansas. These eggs 

 were buried some ten inches below the surface, in the 

 Fall of 1876, in grading the ground around the chemical 

 laboratory. The superincumbent material was clay, old 

 mortar and bits of stone, and a plank sidewalk was laid 

 above all. In removing and regradingthe soil last spring 

 Mr. J. D. Graham noticed that the eggs looked sound and 

 fresh, and they readily hatched upon exposure to normal 

 influences, the species being determined by Prof. Riley 

 from specimens submitted by Mr. Graham. Remarkable 

 as the facts are there can be no question as to their ac- 

 curacy, so that the eggs actually remained unhatched dur- 

 ing nearly four years and a half, or four years longer than 

 is their wont, and this suggests the significant question : 

 How much longer could the eggs of this species, under 

 favoring conditions of dryness and reduced temperature, 

 retain their vitality and power of hatching ? 



Putting all the facts together Mr. Riley concludes that 

 we are as yet absolutely incapable of offering any satis- 

 factory explanation, based on experiment, of the causes 

 which induce exceptional retardation in development 

 among insects. It is a very general rule that a rising 

 temperature stimulates and accelerates growth, while a 

 falling temperature retards and torpifies, and experiments 

 recorded by the author* show that such is the case with 

 regard to the eggs of Caloptcnus spretus. But there are 

 many exceptions to the rule. The eggs of Crustaceans, as 

 Apus and Cypres, are known to have the power of re- 

 sisting drought for six, ten or more years without losing 

 vitality, while in some cases they seem actually to require 

 a certain amount of desiccation before they will hatch. 

 Yet the fact remains that different act differently in this 

 respect. In short, nothing is more patent to the observing 

 naturalist than that species, and, even individuals of the 

 same species, or the progeny of one and the same indi- 

 vidual, act very differently under like external conditions of 

 existence ; or in other words, that temperature, moisture, 

 food, etc., influence them differently. Hence — as has 

 been shown by Semper to be the case with other animals, 

 so it is with insects —changes in the external conditions 

 of existence will not affect the fauna as a whole equally, 

 but will act on individuals. We can understand how this 

 great latitude in susceptibility to like conditions may and 

 does, in the case of exceptional seasons, prove beneficial 

 to the species by preserving the exceptional individuals 

 that display the power to resist the unusual change ; but 

 we shall find ourselves baffled when we come to seek a 

 demonstrable explanation of the cause or causes of such 

 retardation, while the principles of evolution afford us the 

 only hypothetical one at all satisfactory. In the innate 

 property of organism to vary, and in the complex phe- 

 nomena of heredity, we get a glimpse at the cause — a par- 

 tial explanation — of the facts of retarded development ; 

 for the exceptional tendency in the present may be looked 

 upon as a manifestation through atavism of traits which 

 in the past had been more commonly possessed and more 

 essential to the species. 



* — Abstract of a paper tead before the Entomological Section of the 

 A. A. A. S., at Cincinnati. 



* — 9th Rep. Ins. Mo., also 1st Rep., U. S. Entomological Commission. 



ON THE "LIFE DURATION OF THE HETERO- 

 CERA (MOTHS*)." 

 (Abstract.) 



By J. A. Lintner, State Entomologist of New York. 



The subject of life duration of our insects, not having 

 been given special study, so little is known upon it, that 

 the present contribution would not be warranted, were it 

 not that the confession of our ignorance upon the point, 

 may serve as an incentive to its examination. 



It is a difficult field of study, for the observations 

 should be made upon the insects in the natural condi- 

 tions — not in confinement. Even of the latter state, our 

 knowledge is quite limited. Entire broods of species 

 have seldom been reared, except in the Bombycidae and 

 Sphingidae, where the eggs are easily to be obtained. But 

 in the large family of Noctuidae, I do not know that an 

 entire oviposition, or even a considerable part of one, has 

 ever been carried through to the perfect stage, nor have 

 I any personal knowledge of the time, place, manner or 

 duration of copulation among them. 



In the Attacinae of the Bombycidae, the lives of most 

 are brief ; that of the female seldom reaches fifteen days, 

 while in the male it is still shorter. It is longer in the 

 Sphingidae. 



We may best obtain an approximation to the life 

 period of the moths, from reference to the dates when 

 they are observed abroad. The lists published of collec- 

 tions "at sugar," furnish us with the best data. From a 

 list prepared by myself, it appears that a large number 

 of species of Noctuidae were abroad for about one month. 

 Deducting one-third of this time for their probable un- 

 equal emergence from the pupae, there would remain a 

 term of three weeks for their approximate life duration. 



Mr. W. L, Devereaux, of Clyde, N. Y., from his ob- 

 servations, also infers, " that most of the species remain 

 for about a month." 



As would be expected from so heterogeneous a family 

 as the Noctuidae, the different groups present different 

 life periods. The genera Xylina, Homoptera and Cato- 

 cala, are found to have a considerably longer continuance 

 than that above given. Three species of Xylina were 

 observed by me for forty-one, forty-seven and fifty-one 

 days; ten species of Catocala, for an average of forty-five 

 days ; and nine species of the same genus, as reported by 

 Mr. Devereaux, for fifty-seven days. 



In view of the benefits which would result to Ento- 

 mology, it is suggested, that in future lists published of 

 our insects, the different dates at which they are observed 

 throughout the year, be included. It would aid us in de- 

 termining life duration — would indicate the time when to 

 guard against the commencement of insect attack — when 

 to commit our crops to the ground — when to search for 

 specimens for our cabinets— in short, it would furnish an 

 essential part of the life histories of our species. 



Mr. G. Fasoldt says, in a letter to the American 

 Journal of Microscopy : — 



I have ruled plates up to 1,000,000 lines to the inch, 

 one of which was purchased by the United States Gov- 

 ernment at Washington. 



These plates show lines truly and fairly ruled, as far 

 as lenses are able to resolve, and above this point the 

 spectral appearance of the bands in regular succeeding 

 colors (when examined as an opaque object) shows, be- 

 yond doubt, that each band contains fairly ruled lines up 

 to the 1,000,000 band. 



I do not believe that I will ever attempt to rule higher 

 than 1,000,000 lines per inch, as from my practical ex- 

 perience and judgment, I have concluded that that is the 

 limit of ruling. 



* Read before the A. A. A. S., Cincinnati, 1881. 



