NUMBER. 159 



are of no importance to the forester ; such are the stag-beetle 

 (Lucanus cervus, L.), and many species of Anobiidae and 

 Cerambycidae. 



Many insects confine their attacks to fully-grown or old 

 trees ; others attack only young plants (Plylobius abietis, L.) ; 

 others attack trees of all ages (Myelophilus piniperda, L.). 



The attack may be on the roots (Gryllotalpa vulgaris,.~L., 

 Melolontha vulgaris, Fabr., in the larval state) ; on the bark 

 (most species of Tomicus and Hylesinus) ; on the wood 

 itself (Trypodendron lineatum, Gyll., species of Sir ex and 

 Cerambyx) ; on the leaves or needles (Clirysomela and 

 most lepidopterous larvae) ; on buds (Curculionidae, Tortrix 

 buoliana, Schiff.) ; on the blossom (Anthonomuspomorum^.} ; on 

 fruits (Balaninus mtcttw, L., Carpocapsa pomonella, L., Tortrix 

 strobillcla, L.) ; on the pith (Myelophilus piniperda, L.). 



Many insects by biting and sucking produce malformations 

 termed galls on leaves, shoots, fruits, etc. (Cynips, Aphis, 

 Cecidomyia, Chermes and Coccidae, etc.) ; such damage is easily 

 discernible, but is of subordinate importance. 



Damage by insects reduces the production of good seed by 

 the trees attacked. Dr. A. Hosaeus investigated the seed of 

 Scots pine from trees attacked by and free from leaf-larvae, 

 obtaining 1 and 45 per cent, of good seed respectively. 



SECTION IV. NUMBER. 



The number of individuals of a particular insect that may 

 coexist is in many species limited, but in others may attain 

 vast proportions, especially under favourable circumstances. 

 Thus in 1884,* 200 square miles of sal forest (Slwrea robusta) 

 in Assam, north of the Bramaputra river, were ravaged by 

 the caterpillars of Dasychira Thwaitesi, the trees exhibiting 

 complete or partial defoliation. The appearance of certain 

 insects shows a periodicity, corresponding to the eleven years' 

 weather periods. 



Fortunately, the most prolific of insects, plant-lice, are not 

 the most destructive to forests ; these creatures, according to 

 Reaumur, may produce 5,000 millions from one female in the 



* " Indian Forester," vol. xx., p. 256. 



