Pakt I.] Beeson : Life-History of Diapus furtivus, Sampson. 13 
accumulated before tbe first batch has hatched. It has not been possible 
to ascertain the total number of eggs laid by one female during the 
course of her life, but, from countings of families in more advanced stages 
of development, it is known that the total exceeds 100. 
The newly hatched larva differs slightly in form from the older 
larva but in all stages it is remarkably active and able to travel through¬ 
out all the galleries as fast as the parent beetles. The young larva 
uses its jaws as well as its abdomen for locomotion and progresses along 
the walls of the tunnel without difficulty. After two or three moults 
it has grown large enough to touch the whole circumference of the tunnel 
with its body and uses the rows of tubercles on the abdomen and a 
narrow chitinized plate on the thorax as means of propulsion. The 
larvae spend their lives wandering about the galleries, feeding on the 
sap and the food fungus, which grows on the walls. They take no part 
in the excavation of the galleries. 
Food Material. 
The Platypodidae, like the genera Xyleborus and Corthylus of the 
family Ipidae, are true ambrosia beetles, i.e., the principal food of the 
larvae is a fungus, the ambrosia, which lines the walls of the brood- 
tunnels in a thin felt-like layer of mycelium and clusters of cells. The 
ambrosia of Diajpus furtivus is not very abundantly developed and is 
frequently absent from some of the branch galleries. It appears as 
a light grey layer of variable thickness covering the surface of the 
galleries, which rapidly become black in color. The black stain pene¬ 
trates into the surrounding wood tissue and forms a zone J to | of an 
inch in width on either side of the gallery. The black stromatic growth 
of a fungus penetrates the wood tissue and blocks up the vessels and 
medullary rays (Plate II, /). 
The discoloration appears to be connected with the ambrosia fungus, 
but, whether due to it or an associated species, has not been determined. 
The newly excavated galleries are not discolored but, in the course 
of a week or two, the stain makes its appearance and the width of the 
blackened zone gradually increases with the age of the gallery. It 
may be pointed out that the discoloration is characteristic of the gal¬ 
leries of Diajpus furtivus. Many other shot-hole borers associated with 
Diajpus furtivus in Sal, e.g ., species of Xyleborus, show no discoloration 
of the woody tissues near their galleries, while species of Platyjpus , Crosso - 
tarsus and Diajpus quinquesjpinatus exhibit it in a much less marked 
degree. 
[ 1 UNIVERSITY DF ILUHCiS LIBRARY 
MAY 2 9 1922 
