THELAXES DRYOPHILA. 13 



value of the observations will remain intact ; and this 

 substitution I would suggest to the author of the 

 paper. 



Kaltenbach, in describing the genus Vacuna, states 

 that the winged females seldom make their appearance, 

 and then only late in summer, and that these lay eggs : 

 further he remarks that in this respect Vacuna 

 resembles the genus Phylloxera.* 



Again, he says the winged forms appear at the end 

 of August in insignificant numbers, and that then they 

 may be found sitting under the leaves, surrounded by 

 eggs in concentric circles. This is true of Phylloxera 

 quercus, but the fact may be doubted as to Thelaxes 

 (Vacuna) ; at least no winged female Aphis has yet 

 been shown to be truly oviparous. 



The galls on the leaves of the oak are occasionally 

 tenanted, not only by Cynipidse, but also by the larvaa 

 of Thelaxes dryophila. These Aphides take no part in 

 forming such " oak-apples "; but they seek shelter and 

 hide in their recesses, chiefly for the large quantity of 

 sap collected in the masses. In Italy Passerinif has 

 noticed the same habit. " Occurrit in quadam galla 

 turbinato-calyciformi quercus," &c. 



Aphides have also been observed to nest within 

 certain galls on the evergreen oak, Quercus ilex, near 

 Florence. 



Some of the Hemerobiidaa prey on the larvas, and 

 the eggs are greedily devoured by a species of Scymnus. 

 Mr. J. Walker counted upwards of one thousand larvas 

 of Thelaxes under one oak-leaf in the Isle of Man. 

 This large number was reduced to ten individuals 

 within the space of two days through the voracity of 

 one single Scymnus caterpillar. 



I here add a few remarks on the general anatomy of 

 Thelaxes dryophila. The alimentary canal is short and 



* " In der Forfcpflanzungsweise sckeinen sie der Gattung Phylloxera 

 nake zu steken, mit der sie auck die eigentkumlicke Fliigellage gemein 

 kaken." Kalt., ' Mon. der Pflanzenlause,' p. 177. 



f Pass., ' Apkid. Italicae,' p. 83. 



