A HISTORY OF SURREY 



on which it feeds. A beneficent thunderstorm or the ravages of numerous 

 lady-birds, lace-flies and small Hymenoptera, all by their several actions, 

 reduce this exuberant insect-life to its proper dimensions. Several root- 

 feeding aphides are found in our gardens, as A. subterranea, Scbizoneura 

 fodiens, and Tychea pbaseoli on the French bean, but the injuries done 

 bear no proportion to those done by aerial forms to the green leaves. 



Ornamental flowers. Although it cannot be said that every plant 

 has its own special aphis ready to attack it, the appended list may point 

 out the fact that so far as observation goes certain aphides are only to be 

 found on particular plants and trees. Thus Rhopalosiphum nymphace is 

 believed to be exclusively connected with the water-lily, which suffers 

 much from its attacks ; Aphis opima seems truly to poison the sap of our 

 greenhouse cineraria ; Callipterus castanea I have only found on the sweet 

 chestnut ; Pteroc allis jugla ndicola only affects the walnut ; Chermes abietis 

 only the spruce fir and C. laricis the larch. But it is highly probable 

 that in many cases a stint of the natural food may cause a taste for a 

 plant of quite a different family. There is no strict rule which can be 

 followed in this respect. British aphides are found even to affect plants 

 indigenous to the cultivated parts of India. Siphonophora pelargonii and 

 S. rosce are the common pests of our geraniums and calceolarias ; Aphis 

 papaveris blackens the stalks of our poppies ; Siphonophora rosce, S. rosarum 

 and S. trirhoda encrust the soft shoots of our choice roses, besides which 

 other species infest the columbine, honeysuckle and other ornamental 

 flowering plants. 



Forest trees. Notwithstanding the astringency of the leaves of the 

 English oak they form the food of at least five species of aphis, the most 

 prevalent of which are Callipterus quercus and Thelaxes dryophila. The 

 finely clouded membranous wings of Dryobius roboris and of D. croaticus 

 will separate these species from the former ones. They are also remarkable 

 for the fine purple-red stain they give to alcohol and to turpentine spirit 

 when insects are soaked in them. Stomaphis quercus is an example of a 

 dying-out or defunct species ; it is remarkable for its very long and ex- 

 tended proboscis furnished with fine bristles, used for piercing the sap- 

 wood of Quercus sessifolia. It is perhaps the largest aphis yet described, 

 and is very rare. Specimens were captured by F. Walker about 1850 on 

 some oaks near Weybridge, at Dulwich and also at Finchley. 



The linden or lime tree shelters very many thousands of Pterocallis 

 tiliee under its leaves. These insects, common in Surrey, occur on the 

 continent in such profusion, and eject from their nectaries such a quan- 

 tity of honeydew, that Boussingault the French chemist stated that one 

 sick tree alone will produce three kilograms of the sweet liquid, and 

 Kaltenbach says that in Switzerland the traveller may trace this aphis by 

 the viscid substance which it sheds on the ground. P. tiliee is the prey 

 of numerous parasitic Hymenoptera, twenty or more individuals being 

 sometimes contained in the body of a single specimen. Another species 

 of this genus, P. fagi, forms small companies which make the common 

 beech almost hoary with the cottony covering of their bodies. The 



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