342 



FARMERS' REGISTER— ON THE GENERATION OF INSECTS. 



ishment, lencrthened out parts of its body into 

 arms and other members. For example, alter 

 this filament had improved itself into an oyster, 

 and been by chance left dry by the ebbing of the 

 tide, its efforts to reach the water again expanded 

 the parts nearest to the sea into arms and legs. If 

 it tried to rise from its native rocks, the efforts 

 produced wings, and it became an insect, which in 

 due course of time imi)roved itself by fresh efforts 

 till it became a bird, the more perfect members 

 being always hereditarily transmitted to the pro- 

 geny. The different forms of the bills of birds, 

 whether hooked, broad, or long, were, he says, 

 gradually acquired by the perpetual endeavors of 

 the creatures to supply their wants. The long- 

 legged water-foAvl ( Grallatares, Vigors) in this 

 way acciuired length of legs sufficient to elevate 

 their bodies above the water in which they waded. 

 "A proboscis," he says, "of admirable structure 

 has thus been acquired by the bee, the moth, and 

 the humming-bird, for the purpose of plundering 

 the nectaries of ffowers."* Lamarck, an eminent 

 French naturalist, recently deceased, adopted the 

 same visions; and, among other illustrations of a 

 similar cast, he tells us that the giraffe acquired its 

 long neck by its efforts to browse on the high 

 branches of trees, which, after the lapse of a few 

 thousand years, it successfully accomplished. 



Theories like the preceding all originate in the 

 endeavors of human ingenuity to trace the opera- 

 tions of nature farther than ascertained facts will 

 warrant; and the necessaiy blanks in such a system, 

 which presupposes much that cannot be explain- 

 ed, are filled up by the imagination. This inabil- 

 ity to trace the origin of minute plants and insects 

 led to the doctrine of what is called spontaneous 

 or equivocal generation, of which the fancies 

 abovementioned are some of the prominent bran- 

 ches. The expernnents of Redi on the hatching of 

 insects from eggs, which were published at Flor- 

 ence in 1668, first brought discredit upon this doc- 

 trine, though it had always a lew eminent disci- 

 ples. At present it is maintained by a considera- 

 ble number of distinguished naturalists, such as 

 Blumenbach, Cuvier, Bory de St. Vincent, R. 

 Brown, &c. "The notion of spontaneous gene- 

 ration," says Bory, "is at first revolting to a ration- 

 al mind, but it is, notwithstanding, demonstrable 

 by the microscope. The fact is averred: Muller 

 has seen it, I have seen it, and twenty other obser- 

 vers have seen it: the Pandorinia exhibit it every 

 instant.t" These pandorinia he elsewhere de- 

 scribes as probably nothing more than "animated 

 scions of Zoocarpse" (propagules animesdes Zo- 

 ocarpes.J) It would be unprofitable to go into 

 any lengthened discussion upon this mysterious 

 subject; and we have great doubts whether the 

 ocular demonstration by the microscope would suc- 

 ceed except in the hands of a disciple of the school. 

 Even with naturalists, whose business it is to deal 

 with facts, the reason is often wonderfully influenced 

 by the imagination. 



But the question immediately before us happily 

 docs not involve these recondite discussions; for if 

 even pandorinia and other animalcules were proved 



* Darwin's Zoonomia, sect, xxxix. 3d edit. London, 

 1801. 



fCict. Classique d' Hist. Nat., Art. Microscopiques, 

 p. 541. 



JDict. Class., Art. Pandorinees. 



beyond a doubt to originate in the play of chemi- 

 cal affinities or galvanic actions — (a more refined 

 process, it must be confessed, than Kircher's chop- 

 ped snakes,) it woulJ not effect our doctrine that 

 all insects are hatched from eggs; lor no natualists of 

 the present day classes such animalcules among 

 insects. Leaving animalcules and zoo])hytes, 

 therefore, out of the question, we have only to ex- 

 amine such branches of the theory of spontaneous 

 generation as seems to involve the propagation of 

 genuine insects, — like the fancies about putrefac- 

 tion which we have seen refuted. 



The notion that small insects, such as aphides 

 and the leaf-rolling caterpillars, are spread about 

 or rather generated, by what is termed blitr/tt (pos- 

 sibly from the Belgic blinkan, to strike with light- 

 ning,) is almost universally believed even by the 

 most intelligent, if they have not particularly stu- 

 died the habits of insects. JVlr. Main, of Chelsea, 

 an ingenious and well-informed gardener and nat- 

 uralist, describes this as an "easterly wind, attend- 

 ed b}' a blue mist. The latter is called a blight, 

 and many people imagine that the aphides are 

 wafted through the air by this same mist.*" "The 

 farmer," says Keith, "supposes these insects are 

 wafted to him on the east wind, while they are 

 only generated in the extravasated juices as form- 

 ing a proper nidus for their eggs.j" A more de- 

 tailed account, however, is given by the late Dr. 

 Mason Good, and as he speaks in part from per- 

 sonal observation, and was not only one of the 

 most learned men of his time, but an excellent 

 general naturalist, his testimony merits every at- 

 tention: — 



"That the atmosphere," says Dr. Good, "is 

 fi-eighted with myriads of insect eggsthatelude our 

 senses, and that such eggs, when they meet with 

 a proper bed are hatched in few hours into a per- 

 fect form, is clear to any one who has attended to 

 the rapid and wonderful effects of what, in com- 

 mon language, is called a blight upon plantations 

 and gardens. I have seen, as probably many v/ho 

 read this work have also, a hop-ground complete- 

 ly overrun and desolated by the aphis himiitU, or 

 hop greenlouse, within twelve hours after a honey- 

 dew (which is a peculiar haze or mist loaded with 

 poisonous miasm) has slowly swept through the 

 plantation, and stimulated the leaves of the hop to 

 the morbid secretion of a saccharine and viscid 

 juice, which, while it destroys the j^oung shoots 

 iDy exhaustion, renders them a favorite resort for 

 this insect, and a cherishing nidus for myriads of 

 little dots that are its eggs. The latter are hatch- 

 ed within eight and forty hours after their deposite, 

 and succeeded by hosts of other eggs of the same 

 kind; or, if the blight take place in an early part of 

 the autumn, by hosts of the young insects pro- 

 ducted viviparously; for, in different seasons of 

 the year, the aphis^ breeds both way?. Now it is 

 highly probable that there are minute eggs, or 

 ovula, of innumerable kinds of animalcules float- 

 ing by myriads of myriads llirough the atmosphere, 

 so diminutive as to bear no larger proportion to the 

 eggs of the aphis than these bear to those of the 

 wren or the hedge-sparrow; protected at the same 

 time from destruction, by the filmy integument that 

 surrounds them, till they can meet with a proper 

 nest for their reception, and a proper stimulating 



♦London's Mag. of Nat. Hist. i. 180. 

 tKeith's Physiological Botany, ii. 486. 



