INSECT AND FUNGOID ENEMIES 169 



Tortrix Viridana (Green Tortrix Moth). The cater- 

 pillars of this moth are about the worst enemies of the 

 Oak, as they often defoliate acres of Oak woods in May 

 and June. They are dirty grey in colour, with four small 

 black spots upon each segment, and are about f inch long 

 when full fed. The moth is a very pretty little insect. 

 Its forewings are like bright green satin and lightly fringed. 

 The hindwings are light grey. The width across the 

 wings is about J inch. Starlings and rooks will congre- 

 gate in thousands to feed upon the caterpillars; which 

 shows how useful these birds are. 



Gall Insects. 



The late Mr. Gillanders in his book " Forest Entomo- 

 logy " gives twenty- four different gall insects on Oak. 

 These insects, or " midges," lay their eggs upon the 

 leaves, flowers, twigs, or roots, and, by some process or 

 other that has never really been explained, the sap forms 

 a gall round the egg or the hatched larvae, which enlarges 

 as the latter grows. J?or each different gall insect there 

 is a different-shaped gall. The most common ones are 

 those of the following " midges ": 



Cynips Kollari (the Marble Gall). The larvse may 

 easily be found by cutting open a marble. 



Teras Terminalis (Oak- Apple). Common in all parts 

 of the country. The alternate generation of this insect 

 causes a gall on the roots of the Oak-trees called Biorhiza 

 aptera. This gall resembles the honeycomb of the bumble 

 bee. 



Dryophanta Divisa. Small round galls on the veins on 



