340 ANTS. 



nests in the immediate vicinity of the aphid droves or actually keep 

 them in their ne>t> or in " sheds " carefully constructed for the purpose. 



Nearly all plants except the cryptogams, may be infested by aphid-, 

 and no part of the plant is free from their attacks. Certain species 

 prefer the leaver, others the twigs, and still others the roots and subter- 

 ranean stem-. .Most species live on the surfaces of the plants but a 

 number also make and inhabit galls. Only the former, of course, are 

 acro-ible to the ants. The sedentary and gregarious habits of the 

 aphids also expose them to a host of enemies, among which the Coc- 

 cinellid beetles and their larvae, the larvae of certain Diptera (Syrphidae) 

 and Xeuroptera (Chrysopa, Heinerobius) and a host of small parasitic 

 II vmenoptera ( Pteromalidae, Braconidse, Crabronidse) are the most 

 formidable. 



The aphids pierce the integument of the plant with their slender, 

 pointed mouth-parts and imbibe the juices which consist of water con- 



FIG. 204. Portion of tap-root of wormwood (Artemisia vnlgnris) with Lasius 

 umbratus workers attending young and adult plant-lice (Trama radicis). (Mord- 

 wilko.) a. Sucking adult Trama with hind legs raised : b. ant palpating Trama with 

 her feelers ; r, ant receiving droplet of honey-dew from anus of Trama ; d and e, 

 ants carrying away plant-lice in their jaws; /, Trama with droplet of honey-dew 

 suspended from perianal hairs. 



taining in solution cane sugar, invert sugar, dextrin and a small amount 

 of albuminous substance. In the alimentary tract of the insects much 

 of the cane sugar is split up to form invert sugar, and a relatively small 

 amount of all the substances is assimilated, so that the excrement is 

 not only abundant but contains more invert and less cane sugar than 

 the juice- of the plant. This excrement is voided in colorless drops, 

 and when it falls on the leaves of the plants and dries in the air is 

 known as " honey-dew," the ros incllcns, me! acriuin. roscida niello, 

 nicllif/ti, "HV ///A; of the ancient writers. Reaumur (1737) and Leche 

 ( 17(15 ) seem to have been the first to ascertain that the honey-dew, 

 which the ancient- -uppo-ud to come from the plants, from the sky or 



