pregnated through absorption of the spermatozoa, which enter their walls, imparting 

 to them vitality. The internal organs of the male are tubular vesicles, or testes, 

 which secrete the seminal fluid, which by means of the intromittent organ is intro- 

 duced into the spermatothecse of the female. Union between the sexes among 

 insects generally takes place but once, and is not recurrent. The female, having 

 been impregnated, proceeds at once to lay her eggs upon the tender leaves or the 

 bark of the plants upon which her progeny are to be nourished, and then promptly 

 dies. The life of insects in the winged form is usually very brief. Inasmuch as 

 there are great differences between the sexes in insects alike in size, form, color, and 

 markings, it is well for the collector to carefully preserve specimens which may be 

 captured in copulation. Such specimens should be designated as "Taken in coitu." 

 The writer in such cases uses the formula "A c? in coitu with B 9 ," which is put in 

 minute handwriting upon a label and placed upon the pin bearing the male insect. 

 Upon the pin carrying the female insect there is put the label "B 9 in coitu with 

 Ac? 1 ." The finding of insects in copula is sometimes the only way in which to def- 

 initely settle the question of sexual relationship between forms. So different are 

 some insects that the two sexes have in a number of cases been described by early 

 writers as belonging not merely to different species, but to different genera, and 

 even families. 



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