218 MR WALTER RITCHIE ON THE STRUCTURE, BIONOMICS, AND 
parts slightly out of position, and without cover-glasses or pressure ; preparations 
boiled in caustic potash, and untreated natural preparations, and without satisfactory 
differentiating results. In some cases it seemed that the shape of the labral edge of 
the clypeus — straight-edged or more rounded — would prove a helpful character for 
distinction, but examination of a large series of specimens proved that one could not 
rely absolutely on this character. 
The close resemblance between the larvae of the two species is not difficult to 
understand, as not only are they very near to one another in actual relationship, but 
their food habits are practically identical, both living below the bark and tunnelling 
in the bark and sometimes in the outermost layers of the sapwood. 
The Pujpa. 
The pupa of M. minor in general size and form resembles the adult insect. It is 
white in colour, but soon becomes darker brown. The darkening. of colour first reveals 
itself in the eyes, which show as two black spots, and in the mandibles, which show 
as two dark -brown patches. 
In a ventral view of the pupa (fig. 12) the chief divisions of the body and their 
appendages are visible. 
The vertex or front portion of the head bears on either side of it a few very 
small spines ( fs .) which are widely separated from one another. On each side of 
the head region there is present the antenna (a.), at the anterior base of which is 
situated the eye (e.). Posterior to the base of the antenna lies the gena (g.) or cheek 
region. Between the gense lies the labrum ( l .) or upper lip and the other mouth 
parts, viz. the mandibles ( m .), the 1st maxillse (mx.), and labium (U.). 
The three pairs of legs are folded along the surface of the body, the last pair more 
or less overlapped by the elytra and wings (el. and w.), only the coxae (d) and 
femora ( h ) being visible. The femora of the 1st and 2nd pairs of legs show small 
projecting spines ( fsp .) on their apical parts. Between the coxae of the last pair of 
legs is situated the intercoxal area (i.a.). 
Of the thorax the meso- and metasternum is visible ; a deep groove (o) runs up 
the centre of the last-named portion. 
Of the abdomen the sternal parts of the last eight segments are visible : the 9th 
segment bears two prominent fleshy projections or spines ( c.s .), the presence of which 
is characteristic of Scolytid pupae ; the 10th segment (r) appears only as an oval 
patch intersected by grooves. On either side of the body the elytra (el.) are situated, 
while from under them project the tips of the flying wings (w.). 
In the dorsal aspect of the pupa the noteworthy characters are the lateral spines 
on the pronotum, the scutellum at the base of the elytra, two rows of small 
fleshy spines along the dorsal part of the abdominal segments, and usually three 
rows of small fleshy spines — the pleural spines — parallel to the sides of the body. 
