OBSERVATIONS ON THE ENTOMOLOGY OF THE SCOTS PINE. II5 



Pityogenes bidentattis, two of our commonest pine beetles 

 (Plate XII. figs. 2b and 4^). 



The tribe Hylesinina consists of eight genera, only two of 

 which, however, call for consideration here. These are the 

 genus Myelophilus and the genus Hylastes. These two genera 

 can be recognised by the number of joints in the middle part of 

 the antennae, known as the whip, and in the shape of the apical 

 part or club. In Myelophilus the whip consists of six joints, and 

 the club is roundly ovate. In Hylastes the whip is seven-jointed, 

 and the club is ovate but slightly acuminate (Figs. \a and 2a). 

 This is a somewhat difficult distinction to make in the field, 

 and the general conformation of the beetles may have to be 

 relied on. The members of the genus Myelophilus are somewhat 

 larger, less cylindrical, and more hairy ; those of the genus 

 Hylastes are generally more elongate and narrow in form. In 

 Hylastes, too, the pro-thorax is generally longer in proportion to 

 the wing-covers. These, however, are only general and therefore 

 somewhat doubtful distinctions, and for certain identification 

 of the genera the antennae must be relied on. 



The genus Myelophilus is represented by two species, both of 

 which occur on Scots pine, namely, Myelophilus piniperda and 

 Myelophilus minor. Only the first of these, so far as is known, 

 is generally distributed in Scotland, and it will be sufficient to 

 indicate its chief point of difference with M. minor. This lies 

 in the wing-covers or elytra. In M. piniperda the row of bristles 

 lying in the second interstice or groove of the wing-cover is not 

 prolonged to the apex, but stops just a little behind. In M. 

 minor this row of bristles is continued right to the apex. 



The genus Hylastes is represented by five species, only two 

 of which, however, appear to be common on Scots pine, namely, 

 Hylastes palliatus and Hylastes ater. H. palliatus is the smaller 

 beetle, and in general appearance it is stouter and shorter than 

 H. ater. It is brown in colour, and the pro-thorax is bluntly 

 pear-shaped. H. ater is long and cylindrical in appearance, and 

 is, when fully matured, dull black in colour. In it the thorax is 

 narrowly oval in shape. 



Of the Dryocsetina tribe three species belonging to three 

 different genera are the commonest representatives, namely, 

 Trypodendron lineatum, Tomicus acuminaius, and Pityogenes 

 bidentatus. T. lineatum is included here less on account of its 

 economic importance than on account of its peculiar habits. In 



