1 74 TRANSACTIONS OF THE ILLINOIS 



57. Lachnus ulmi, Uxnn. The Elm Lachnus. 



On the under side of elm leaves. 



58. Lachnus populi, Linn. The Poplar Lachnus. 



On the under side of the young leaves of the Populus grandidentata. 



In addition to the species already named which belong to this sub- 

 family, {Ap/ndincB,) I mention the following European species found on 

 cultivated plants, which have been introduced into this country, and 

 which, if they have not already brought them, will sooner or later bring 

 hither their native plant-lice. 



59. Aphis dauci, Fabr. {A. plantaginis , Schrank.) The Carrot Plant- 



louse. 



Infests the umbels of the carrot. 



60. Aphis pastinaccE, Linn. {A. caprece, Fabr.) The Parsnip Plant- 



louse. 



Infests the stems and leaves of the parsnip. 



61. Lachnus pini, Linn. The Pine-tree Lachnus. 



62. Lachnus abietiSj^aSk. {Aphis abietis,^d\\i.') The Fir-tree Lachnus. 



Possibly same as L. abietis, Fitch. 

 03. Lachnus laricis, Walk. The Larch-tree Lachnus. 



64. Lachnus juniperi, Fabr. The Juniper Lachnus. 



65. Siphonophora absinthii, Linn. {Aphis tanaceti, Linn.) 



Found on the stems of common tansy, and some other aromatic 

 plants. 



66. Siphonophora rubi, Kalt. 



Found on blackberry bushes, or plants closely allied thereto. 



67. Siphonophora fragarice,^\di\\i. The Strawberry Plant-louse. 



NATURAL ENEMIES. 



There is perhaps no other group of insects in the entire class that has 

 as many natural and inveterate foes, as that which includes the true Plant- 

 lice. These species appear to be designed by nature to extract the sap 

 of plants and fit it for the nourishment of other insects. Living entirely 

 upon the sap of the leaf, twig or stem on which they are deposited, and 

 having little occasion for exercise or movements, and led by instinct to 

 avoid as far as possible the direct rays of the sun, their external envelope 



