Part .VII] Beeson: Life History of Toon Borer. 
17 
the attack is unsuccessful; and a flow of sap or gum results, which may 
entrap and drown the larva. Constant tapping of sap apparently weakens 
the shoot, and the larva eventually gains entrance. Once established 
within the shoot, the larva excavates a central gallery in the pith, which 
is increased gradually during the feeding period until it may attain a 
length of two feet. The larva usually remains in one shoot during the 
course of its life, but under certain conditions, as for example, in stunted 
rapidly killed shoots, the larva of later instars abandons its original 
galley, and attacks a second shoot, boring in at a spot where the epi- 
dermis is more suberised or at the axil of a leaf or smaller twig. A 
gummy mass of frass and excreta bound up with silk webbing marks 
the site of the entrance hole, [vide Plate IV, fig. 13.] 
The shoot above the entrance hole dies or shrivels, eventually falling 
over or breaking off at the point of weakness. Below the site of entry, 
the shoot with its buds and lateral shoots dies and dries up as far down¬ 
wards as the gallery extends. [vide Plate IV, fig. 15.] 
Within the shoot the larva constructs at intervals partitions of silk 
[vide Plate IV, fig. 14], which act as a safeguard against the entrance 
of predaceous insects and parasites, and also keep out rain-water. 
The combined work of the third and fourth broods kills off the shoot 
growth of the year, while the fifth brood larvae are in a position to attack, 
any new shoots that may be put out by the tree after the rains have 
ceased. The aggregate effect is a complete cessation of height-growth 
and the production of bunches of stunted witches’-broom -1 ike shoots. 
In certain cases, especially among the fifth brood larvae, the gallery 
may be continued down into stems of the previous years’ growth. Such 
stems, although hollowed out do not as a rule die back. 
After the emergence of the moths the hollow portions of stems are 
occupied by various insects, e.g., many species of ants ( Formicidce ), bees 
(Apidce) and wasps ( Sphegidce ), which delay the occlusion of injured 
tissues. 
Pupation. The third, fourth and fifth brood larvae pupate towards 
the base of the hollowed shoot after constructing at least one partition 
of silk in addition to the cocoon. Fifth brood larvae which hibernate 
without pupation invariably construct silken hibernacula. 
Pupal and imaginal habits. 
1. Habits of the Pupa. 
The cocoon. The location of the pupa has already been alluded 
to. In the first and second generations, pupation takes place in con¬ 
cealment under bark flakes or in accidental shelters ; in the third, fourth, 
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