June, 1920.] ClIAMnF.RLIX : W'OOD-BORING BEETLES. 153 



Seasox.vl History. 



The eggs are deposited in crevices of the bark in late April and 

 May, in the vicinity of Corvallis;- the minute larvx enter the bark, 

 work to the cambium and extend their mines through the cambium, 

 bark or wood during the summer, fall and winter. Pupation takes 

 place in ^larch or April and lasts from two to three weeks. Jhe 

 first adults were noted April i6. 



Work and Habits. 

 The hal)its of the hirv?e differ, some work only a sliort time in the 

 cambium, excavating their characteristic oval tunnels whicli are about 

 three-fourths in the bark and one-fourth in the wood; they then enter 

 the sapwood and often work into the heart wood; others seem to 

 spend almost their entire larval stage in the cambium. Just prior to 

 pupation the larva digs to the outer portion of the bark, leaving a 

 thin covering over the future exit hole. From here the larva in- 

 variably returns to the sapwood to pupate. From one-fourth to one- 

 half an inch below the cambium will he found the pupal cell, which 

 measures from 7 to lo mm. in width and 12 to 15 mm. long, always 

 parallel to the surface and with the grain of the wood. The mines 

 are packed with borings and excrement but lack the concentric ap- 

 pearance of the packings in the mines of many of the group. 



Parasites. 



The most important parasite of this beetle seem to be a predacious 

 mite Pcdiculoidcs vcntricosus.^ These mites w'ere found in great 

 numbers on both larv^ and pupce. The males are hardly visible to the 

 unaided eye, while the females appear as small spherical yellow bodies, 

 which might be taken for eggs; the largest are almost one mm. in 

 diameter. The extent of the ravages of these mites may be judged 

 from the following experiments. 



2 Elevation 400 ft. Latitude 44° 32'. N. Longitude 123° 16' \\. 



3 This peculiar species belongs to the small family T ARSON EM I D JE . The 

 male and female differ radically. The female when mature has the abdomen 

 enormously swollen so that it is 20 to 100 times greater than the rest of the 

 body due to the mass of eggs within. The eggs hatch and the young grow 

 within the body of the parent and are born sexually mature. The male has 

 almost no abdomen, the body is short and angulate behind. Both sexes possess 

 needle-like mandibles and sucking mouth parts. 



