. Insect transformations . med by Dufour and others, thatthe mothers not only hatch their eggs within the body,but retain them there till they are changed into chry-salides. R aumur gives a lively narrative of hisdiscovery, and the solicitude of his servants to find himfemale flies ready to deposit what he at first took for ♦ IVf. P. ITuber on Ants, p. 245. + Derham, Ihys. Theol. ii, 207. 11th ed, t Phil. Trans. No. xxiii. OVO-VIVIPAROUS FLIES. 117 eggs. He was so anxious to hatch those supposedeggs that he carried I hem in his pocket hy day andtook tlicm to bod with him at night, (as JJonuet
. Insect transformations . med by Dufour and others, thatthe mothers not only hatch their eggs within the body,but retain them there till they are changed into chry-salides. R aumur gives a lively narrative of hisdiscovery, and the solicitude of his servants to find himfemale flies ready to deposit what he at first took for ♦ IVf. P. ITuber on Ants, p. 245. + Derham, Ihys. Theol. ii, 207. 11th ed, t Phil. Trans. No. xxiii. OVO-VIVIPAROUS FLIES. 117 eggs. He was so anxious to hatch those supposedeggs that he carried I hem in his pocket hy day andtook tlicm to bod with him at night, (as JJonuet after-wards did with the eggs of aphides,) f<)r several weekssuccessively; but instead of grubs, as he had expected,perfect flies were evolved exactly similar to their pa-rents. He calls them spider flics, from their resem-blance to spiders; and in some parts of France thespecies which infests horses {Hippobosca equina) iscalled the Spaniard or J3r«ton: in England it is toowell known under the name of the forest Spider flies {Hippoboscidcr, Leach.) We have the more willingly introduced this sub-ject here, that another fly [Crativina Hiriiiulinis,), of the same family, has the instinct to de-posit its egg-like cocoons in the warm feathery nest ofswallows, where they have all the necessary heatwhich R aumur, in his experiments, was so careful tomaintain. In return l<)r the warmth which the vounghas thus received, the perlect fly, during its brief ex-istence, lives by sucking the bluod of the swallows, asthe one first mentioned sucks the blood of horses,horned cattle, and, it is also said, of man. 118 INSECT TRANSFORMATIONS. The effect of heat upon the eggs of insects has beencarried much farther than in the experiments justalluded to of R aumur and Bonnet.* Spallanzaniwas desirous of ascertaining what degree of heat theeggs of insects and other animals, as well as the seedsof plants, would bear when compared with their larvae;and he found that below 93° Fah
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