THE LARCH AND ITS IMPORTANCE IN SWEDISH FOREST ECONOMY. LXXI 
30.9 26 of the trunks and 26.5 & of the timber have been removed. There 
remain here only 246 trunks per hectare with timber amounting to 208 cub. m., 
with a mean diameter of 38.2 cm. at the age of 50. :It is evident that 
the remaining number of trunks is only half that shown in the stand survey 
for the larch (see Table VII), but the volume of timber is two thirds of that 
given in the table. The mean diameter of the stand is 12.5 2 larger than 
that of quality I in stand-survey. This is a striking example of what can 
be obtained by means of thinning. Here, in fact, the crown of the larch, 
:owing to the great interval between the rows, has developed in the same 
way as after heavy thinnings. No injurious effect on the form of the trunk 
or increased crookedness in the trees can be observed. Only 2.8 of the 
total number of trees are crooked, and 6.2 25 have been marked. (c). This 
example, however, speaks strongly in favour of very heavy thinnings in larch 
woods, and goes to show that a futute productivity table for the larch will 
give a much lower number of trunks and a much higher mean diameter than 
is given in the stand-survey on page 644. 
The various things that iniure the larch are treated in a special sec- 
tion F. Brief information is given about the injuries inflicted on the larch by 
wild animals and domestic cattle, after which Doctor Ivar TRÄDGÅRDH gives 
a succinct account on pp. 669—675 of the insect pests that attack the 
larch. — 
Our knowledge of the insect enemies of the larch in Sweden is in several 
respects very insufficient. Therefore, this review must necessarily be very 
summary and can only deal briefly with the more important species known 
to occur in Sweden, besides adding some information regarding a few species 
which, although not yet recorded from Sweden, may probably on further in- 
vestigations be found there. 
In nurseries the young plants are attacked by the same species as other 
trees, as the cutworms (Agrotis sp-), wire-worms, the larvae of cockchafers, 7z- 
pulidae and Bibionidae which injure the roots. 
Young plants are attacked by FPissodes and Magdalis, änd from England 
also injuries caused by Hvlastes ater are recorded, hare no records of in- 
jury done by Hvlobius seem to exist. 
An examination of the list of the bark-beetles of the larch shows that it 
has many of these in common with the spruce-tree, indicating that these trees 
are more closely related than are the larch and the pine tree. The larch is 
thus attacked by ps typographus, Pityogenes chalcographus, Hylurgops palliatus, 
Polygraphus poligraphus and Xvloterus domesticus. The pine-beetles, on the other 
hand, attack the larch only under exceptional circumstances brought about 
by man himself. 
Amongst the longicorns TJetropium castaneum and Anthaxia quadripunctata 
are the most important. 
The larvae of two moths also do injury to the branches. One is Grapholitha 
(Laspeyresia) zebeana, not yet recorded from Sweden, which especially in the 
Alps destroys two-year-old branches by excavating galleries in the bark, caus- 
ing thereby the appearance of galls, the size of a cherry, the twigs in conse- 
quence breaking off and Dasvevpha Willkommtir entering the wonnds. 
The other "is ÅArgyresthia laevigatella, the larva of which makes galleries in 
the bark of the young shoots causing them to die. 
