FOREST IMPORTANCE OF MYELOPHILUS MINOR HART. 
219 
The Brood Galleries of M. minor (fig. 13). 
The brood galleries of M. minor are very characteristic, and, as will be seen by 
reference to fig. 13, it is quite impossible to confuse them with those of M. piniperda. 
Consequently, they are of great aid to the forester, in absence of beetles them- 
selves, helping him to decide which species is at work. The typical mother gallery 
of M. minor is two-armed and runs in the transverse direction. The larval galleries 
run vertically upwards and downwards, and are not quite close to one another. 
There is a variation in the length of the mother galleries in my specimens from 1^ to 
6^ inches. The long mother galleries were found on stems not so badly infested, and 
where therefore the beetles had room to work. The short mother galleries were 
found on very badly infested stems, the mother galleries in these conditions being 
shorter owing to overcrowding. As a rule a long mother gallery did not carry 
with it a larger number of eggs than the number in a shorter gallery : in the shorter 
galleries the eggs were closer together. The larval galleries were short, and at a 
greater distance from one another when the mother galleries were long. 
The larval galleries also varied to some extent in length. The shortest measured 
was f inch in length, while the longest was 1 inch. 
In my observations the female not only made the two-armed gallery in which she 
laid her eggs, but also the entrance portion of the gallery from the outside. While 
the female was in one arm of the gallery I often found the male in the other arm. 
The male works in throwing out the bore meal made by the female. In mono- 
gamous bark-boring species the female appears to do all the work of boring, and 
pairing takes place under cover or with the female half hidden. The female does not 
complete her gallery and then proceed to egg-laying, but lays her eggs in niches 
cut on either side as she continues to tunnel. 
The two-armed gallery is completed in about 25 days to one month. In 50 
separate cases which I recorded in my notebook the number of eggs laid was 21. 
The highest number I ever found was 31. Never in any completed gallery have I 
found a less number than 19. 
When the eggs hatch the larvae proceed to burrow along the inner bark layers at 
right angles to the mother gallery. The gnawed material from which they derive 
nourishment is passed through the alimentary canal. The undigested material is 
passed out behind and may be found lying in the tunnel, partly choking it up. Thus 
if a piece of bark be removed from the stem, the mother and larval galleries are 
very well marked on it. 
When feeding is completed the larvae pupate. Their place of pupation depends 
entirely on the thickness of the stems which have been chosen for brood purposes. 
Where the bark is very thin — for example, nearer the crown of the tree — the full-fed 
larvae tunnel, it may be \ inch into the sapwood, where each larvae excavates a 
bed in which pupation takes place. This pupal bed lies in the longitudinal direction. 
