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8 Farmers’ Bulletin 1197. 
erub form that is responsible for the destruction of the wood. In all 
cases these larvee hatch from eggs laid by the adult beetles. Some 
of these beetles are rarely seen, as they lie concealed during the day 
and deposit their eggs 
at night. 
The adult round- 
headed borer (fig. 5) 
is a rather large beetle, 
shghtly tapering be- 
hind, brown and gray 
mottled, one-half to one 
and one-quarter ‘inches 
long, with quite long 
flexible horns. It places 
the eggs in crevices or 
under scales of the 
bark. From these eggs 
hatch tiny grubs that grow into rather large cylindrical borers 
(fig. 6), from three-quarters to one and one-half inches in length, 
yellowish white in color, and with a pair of strong brownish jaws. 
This is the largest of the borers in recently cut 
wood. The damage to-the wood begins after 
these grubs hatch and bore in through the bark 
and sapwood, feeding. as they go (figs. 3, 7, 8). 
They spend from 40 to 60 days mining in the 
sapwood, reducing it almost to powder, and then 
enter and honeycomb the heartwood by excavat- 
ing long, oval galleries. Two months or more 
pass before there is any external evidence to show 
that the wood is seriously damaged. The boring 
dust expelled through a hole in the outer bark is 
the first and outward evidence of damage. This 
hole is enlarged as the borer increases in size, and 
through it the beetle finally emerges (fig. 7). 
This borer shows a preference for freshly cut 
‘wood, but has been known to attack wood cut five 
months, especially large limbs or sections of the 
trunk when they are in contact with the ground. 
It is the most destructive of the mesquite insects. sy. 10.—Aault beetle 
The fact that a stick 4 inches by 2 feet contained of the flat-headed 
over 60 of these large borers illustrates how thor- nee ves 
ough a honey-combing takes place. 
The powder-post borers, as adult beetles (figs. 9, 11), are small 
to medium sized, short, cylindrical, dark brown to black,.and hard 
shelled. The smaller forms bore through the bark and around the 
=i 
k 
Se 
& 
Fic. 9.—Adult beetle of the large powder-post borer in 
mesquite, Enlarged. 
