18 INSECT TRANSFORMATIONS. 



the leaf by a sponge, for in this case the immediately 

 excreted globules became apparent. 3 * 



In all observations upon insects, and the other 

 minute parts of creation, it is often exceedingly dif- 

 ficult to distinguish between a cause and an effect. 

 The question of the formation of honey-dew appears 

 to us particularly liable to erroneous conclusions; and 

 we therefore venture to mention a few circumstances 

 which seem irreconcilable with Mr Murray's inge- 

 nious theory. The hop fly (Jlphis humuli\ we think, 

 neither does, nor (for want of appropriate organs) 

 can, feed on the honey-dew; and if -it did, this feed- 

 ing would prove rather beneficial than otherwise to 

 the plant, by clearing it from the leaves whose respi- 

 ratory functions it obstructs. So far from feeding on 

 diseased plants, an aphis only selects the youngest 

 and most healthy shoots, into the tender juicy parts of 

 which it thrusts its beak (haustellutn) , which in some 

 species is much longer than the body, and no more 

 fitted for lapping honey-dew than the bill of JEsop's 

 crane was for eating out of a shallow plate. Jn the 

 experiment, tried by Mr Murray, of wiping a leaf, 

 might not the leaf have been previously wounded, 

 perhaps, by the beak of some aphis, and hence the 

 exudation of sap, not honey-dew? and may not the 

 circumstance of his finding the honey-dew on leaves 

 where there were no aphides be accounted for on 

 the principle that the aphides had abandoned, as they 

 always do, the parts covered with their ejecta, unless 

 these fell from insects on some over-hanging branch? 

 It is justly remarked by M. Sauvages, that they 

 are careful to eject the honey-dew to a distance 

 from where they may be feeding. "j" We have now 

 in our study a plant of the Chinese chrysanthemum 

 (Jinthemis Jlrtemisice folia, WILLD.), the young 



* Treatise on Atmospherical Electricity, p. 147, Lond. 1830. 

 t Trans. Soc. Roy. de Montpellier. 



