GKNERA.TION OF INSECTS. 41 7 



destined to be impregnated. The ideca that the females of this genus 

 of moth were parthenogenetic would, however, naturally arise from 

 observation of insulated facts in the singular series of her generative 

 processes. Our science ever presents a picture of truth evolving 

 itself by slow degrees from the misapprehensions of observers. An 

 entomologist collecting the female Psyche in her unusually early 

 arrested stage of metamorphoses, and without cognisance of the 

 singular mode of impregnation, would at first conclude, from the 

 analogy of other moths, that she was a virgin pupa ; and, keeping 

 her carefully insulated, would be astounded by her abundant pro- 

 duction of fertile ova. Or, if ignorant of the peculiar place of her 

 natural oviposition, he might well mistake the shed pupa-case, filled 

 M'ith fertile eggs, for an actual pupa in which such eggs had been 

 developed. 



There are many striking and beautiful manifestations of instinctive 

 prescience in the modes of oviposition, and in the location and 

 attachment of the ova. Observe the actions of the common white 

 butterfly. Her food is the nectar of flowers ; but, after impregna- 

 tion, she flits about with a purpose quite distinct from anything 

 connected with the act of supplying herself with nutriment : if the 

 plant suitable to the food of the larvae to be developed from her eggs 

 happen to be within the range of her flight, it will soon be seen what 

 her object is. The larvce of most Lepidoptera infest, and can only 

 be nourished properly by, the leaves of particular plants : thus, the 

 mulberry is suitable to the silk-worm, and the cabbage to the Pieris 

 brassicce; when that commonest of our butterflies has found the cab- 

 bage, she has attained the end of her quest, and proceeds to the work 

 of oviposition. 



But a more striking illustration is found in the ichneumon-fly, 

 which is remarkable for the great length of the anal appendages. 

 Her food, also, is nectar ; but her chief occupation' in crossing over 

 the leaves of trees and plants, after being impregnated, is to discover 

 the larva that may be lurking in the bend of the folded leaf, pre- 

 paratory to its change into the pupa-state. The ichneumon, by 

 means of her peculiarly long, sharp, and slender ovipositor, pierces 

 the skin of the larva, and in spite of its writhing and the ejection 

 of an acrid fluid, she succeeds in introducing the instrument, and, 

 by divaricating the two parts of the sheath, makes a little canal by 

 which the ova are transmitted and lodged under the skin : sli^ 

 then flies off to seek another. Sometimes the female ichneumon, 

 when she has found a larva, seems to take no notice of it ; and, in 

 that case, it has been found that another ichneumon has previously 

 oviposited there, and, by some peculiar sense, she ascertains that 



