28 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
same time he admits that P. piniphilus and P. harcyniae 
will attack the branches and crown of perfectly healthy trees. 
Authorities are much divided on the question of the “ genera- 
tion”! of the various Pissodes species, but I will leave this matter 
to be dealt with when mentioning each species in detail. 
Generally it may be stated that the larve and not the imagos? 
do the harm. 
Out of the twenty or so species known in entomology, five are 
well known in Britain or the Continent as pests on coniferous 
trees, viz., Pissodes notatus, P. pini, P. piniphilus, P. harcyniae, 
P. piceae. These five I will describe fully, at the same time 
mentioning at shorter length two additional species, ?. scabricollis 
and P, validirostris. 
DETERMINATION OF THE SPECIES. 
Posterior corners of 
prothorax right- Wing - covers with 
angled, or pro- a narrow trans- 
jecting some- verse band behind 
what sharply. their middle—P. ( Wing - covers have 
The upper surface} pint. longitudinal 
of the prothorax rows of large dots 
wrinkled and ae Re meets varying in size— 
covered ie a cae ares we, 12 eee 
number of closely} yerseband behind 
arranged punc-| their middle. Wing - covers have (Dots medium sized 
tures. longitudina | —P. notatus. 
rows of equally 
sized dots. [Pots fine—P, 
validirostris. 
2 > 4 " D ya , 
Beerenaricarners of Beetles black, in ground colour—P. harcyniae. 
the prothorax Beetles, in ground colour, rusty brown—P. piniphilus, 
rounded, and the 
deep punctures| Beetles with a more or less prominent raised middle line on 
not so close to-| the prothorax, generally much smaller than harcyniae, and 
gether. in colour not so black—P, scabricollis. 
A glance through the above table, which, with slight modifica- 
tions (I have added scabricollis) is Nitsche’s, will show that the 
1 «Generation ””—the time comprised between one egg-laying and the egg- 
laying of the next swarm. Generation is annual if only one brood is produced 
in a year; double, if two broods; biennial, if two years are required to com- 
plete a cycle, and so on. 
2 Imago—the adult insect. 
