FOREST IMPORTANCE OF MYELOPHILUS MINOR HART. 
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reproductive organs of minor drawn from preparations made of the dissected-out 
organs. 
Fig. 18. The immature organs, unripe, and before any egg-laying has taken place. 
The imagos after pupation issue through a flight hole in the bark and fly to the 
young shoots at the top of the tree. Into these shoots the young beetles tunnel 
and feed. As a result the reproductive organs fill out, and efficient pairing and 
egg-laying follow. 
It will be specially noticed in this figure that the egg tubes are not separated 
up into ovarian chambers. In the natural preparations the bursa copulatrix and 
slime glands are empty, and white in colour. 
Fig. 19 shows the reproductive organs of a female about to lay. The ‘egg tubes 
here are divided up into ovarian chambers, while in the natural preparation the 
bursa copulatrix and slime glands are somewhat yellow in colour. 
Fig. 20 shows the reproductive organs of a female dissected out while egg-laying 
was in process. Attention may be directed here to the so-called “ corpora lutea.” 
When a ripe egg has passed through the oviduct the epithelial cells collect at the 
base of the egg chamber, showing and remaining as a little heap of degenerate dirty 
yellow tissue. In the natural preparation the bursa copulatrix and slime glands are 
citron yellow in colour. 
Fig. 21 shows the reproductive organs, dissected out for examination, from a 
beetle which had laid its eggs. 
It is noticeable in this figure that, owing to the completion of egg-laying, the 
ovarian chambers are empty (contracted), containing no eggs, and that the. so-called 
corpora lutea is now very conspicuous. In the natural preparation the bursa 
copulatrix and slime glands are dirty yellow in colour. 
Question of Number of Generations in a Year. 
A question which has importance for the forester is whether two generations of 
a bark-boring species are possible in a year or not, a fact which has also to be 
reckoned with in combating these pests. 
From my own observations, both in the open and from experiments, I am 
convinced that in Scotland, in the case of M. minor , the occurrence of a double 
generation in the succession, parents, children, grandchildren in a year, is impossible. 
The following is a short account of my observations from experiments carried out 
during the years 1915 and 1916 : — 
On August 12,' 1915, I was permitted to fell a thirty -year-old Scots pine stem 
on which M. minor had bred. On examination of the galleries on it I found 
immature beetles chiefly, about to emerge from their pupal chambers. No parent 
beetles were present in the mother galleries. I collected these young, immature 
adults as they issued from the bark, and later liberated them in a muslin cage in 
