36 BRITISH APHIDES. 



tibise. They usually contain as many as six ova in 

 various conditions of maturity. 



This Aphis appears to restrict its food to several 

 species of the lime or linden tree. It attacks Tilia 

 rubra, T. jplatyphylla , and T. grandifoUa, the leaves of 

 which shelter thousands on their under sides. They 

 eject the honey-dew in such quantity, that Kaltenbach 

 remarks that the traveller may trace the Aphis by the 

 viscid liquid which it sheds on the ground. In Swit- 

 zerland, the Aphides sometimes almost kill the trees ; 

 and at times so exhaust them of sap, that Boussingault 

 calculates that a single sick tree may produce as much 

 as three kilogrammes of sweet substance, which is 

 entirely the produce of Pterocallis tilicG,^ and elabo- 

 rated from the juice. 



This Aphis, fortunately, is largely destroyed by 

 various parasitic Hymenoptera. As many as twenty- 

 four grubs may sometimes be counted infesting a 

 single Aphis, but at other times one large maggot 

 occupies almost the whole body- cavity, and apparently 

 without attacking the nervous centres, since the host 

 lives on and travels with its guest, as heavy as itself. 

 Such an example, on a smaller scale, I have figured in 

 Vol. II, Plate XLIII, fig. 6. 



The puceron cle tilleul of Reaumur must be referred 

 to a different genus from the ordinary lime Aphis. 

 Eeaumur describes the insects as ranging themselves in 

 single file on one side of the leaf-stalk, and states that 

 by so doing they cause the stalks by their punctures 

 to curve into the form of corkscrews, the growth being 

 arrested on one side only. Reaumur also gives a figure 

 of this distortion. Kaltenbach points out that Linnaeus 

 and Fabricius, both quoted from Reaumur, and this 

 was copied into Miiller's translation of the ' Sy sterna 

 Nature.' Kaltenbach and others long failed to find 

 this "strongly convex" Aphis, which lives in com- 

 panies. Kaltenbach says it cannot be confounded with 



* Vide Boussingault, " On Honey-dew j " vol. i, p. 42, of this Mono- 

 grapli. 



