INSECT PESTS OF PINE AND SPRUCE CONES. CXLI 
Perrista occurred; but one cannot consider this as evidence that the geogra- 
phical distribution of both species is different, as only 200 cones from each 
locality were subject to investigations, which renders the part played by con- 
tingency very great. 
IT) ISKvery. oRarkalle however, that in Northern Sweden Platygaster was 
not bred from those localities — Vargiså, Lycksele, Degerfors and Östra Åsele 
— where Perrista was very abundant, whereas in the South of Sweden an 
high percentage of FPerrisia always corresponded to an high percentage of 
Platygaster. 
The remarkable coincidence of these data seems to justify the inference 
that in the North of Sweden climatic conditions have been favourable to Per- 
rista but not to Platygaster. If this were the case, it would not be surprising, 
other instances being known when certain climatic conditions have favoured 
the reproduction of an insect, at the same time checking that of its 
parasite. 
Table III shows the number of Perrisia strobi and Platygaster contorticornis, 
obtained from 200 cones from 57 localities. From the table it is evident 
that the majority of those localities the cones from which gave a low per- 
centage of Plaiygaster were situated in the North of Sweden, a feature which 
seems to corroborate the above conclusion, that in that part of Sweden the 
climatic conditions were unfavourable to the propagation of Platygaster and at 
the same time points to the possibility of arriving at conclusions of a general 
nature through the investigation of even such a small material as the present. 
The diagram fig. 29 shows the distribution of the localities according to 
the percentage of Perrisia parasitized by Platygaster; from this we see that 
in 25 2 of the localities this percentage was 11—>20, in 13 2 21—30, in 
10 Z 31—40, in 14 Z 41—50 and in 5 & above 50. 
In order to be able to interpret the value of these data, it is obviously 
necessary to know the rate of reproduction of both species, viz., the number 
of eggs laid -by them. It has not been possible to ascertain this; but in this 
connection it is of interest to know that in Platygaster the females are far 
more numerous than the males, while in Perrisia the number of both sexes 
is about equal, which gives Platygaster a certain advantage over Perrisia, 
At Hunneberg and Aspeland we see the last stage in the war between 
Platygaster and its host, not less than 94.8 and 75.9 2 respectively of the 
latter being parasitized by the former. 
Torvmus azureus BuN. 
Although Chalcididae has been repeatedly reared from spruce-tree cones, 
no one suspected them of having phytophagous habits until WACHTL in 1884 
expressed the opinion that some species of Megastigmus found in hips were 
seed-eating and in 1893 proved that this was the case with Megastigmus spermo- 
trophus, a species living in the seeds of Pseudotsuga douglasti. 
In 1909 CROSLY records not less than fifteen different species of seed-eating 
Chalcididae, half of which belonged to the genus Megastigmus, and in 1916 
SEITNER records 12 species of Megastiomus, one of which, Megastigmus abietis 
SEITN., is stated to live in spruce-tree seeds. As RATZEBURG had previously 
described AZ. strobilobius from spruce-tree cones, not less”than two species of 
the genus Afegastigmus have hitherto been obtained from these cones. 
