The Currant-Stkm Girdi^er. 



51 



year had developed full grown borers ; in most cases the eggs ap- 

 parently did not hatch, as no tunnel had been begun in the pith, 

 but in some cases the borers got nearly half grown before they 

 succumbed. As Mr. Marlatt stated, the reason for this great 

 mortality is not apparent. He suggested that it might be due to 

 the fact that the cultivated currant, on account of its difference 

 in growth or greater luxuriance, is not as suitable to the insect as 

 wild currants or allied plants, which were presumably its original 

 food plants. 



Another explanation of this great mortality may be the fact 

 that an unfertilized female will lay eggs and girdle the shoots as 



freely as any other female. We dem- f ^^^^v— 'w^-.^ ^ ■- 



castrated this fact in our cages last *''*^ 



year, but we were not able to definitely 

 determine whether these unfertilized 

 eggs hatched or not. 



However, the fact that there is such 

 a great mortality among the eggs and 

 young grubs of this insect, is of but 

 little practical importance to the cur- 

 rant grower, for in the girdling of the 

 shoots, the pest does its principal 

 injury. 



Extent of the tunnels of the borer ^ and 

 its preparations for the winter. — The 

 grubs begin their work of tunneling 

 down the pith of the girdled shoot as 

 soon as they hatch in the latter part of 

 May. Although the borer continues 

 to work in the pith for about three 

 months.its tunnel rarely extends more thansix inches from the point 

 where the shoot was girdled. In one instance where three shoots 

 branched off, as shown in figure 19, a borer tunneled down to the 

 base of one shoot and then across the main stem and part way up 

 another shoot, where it met its death from the attacks of one 

 of its enemies. 



About September ist, the borer begins to make preparations for 

 the winter a ad for its further transformations- It cleans out the 



q. — Cu.ranL iiioois iplit ipin to 

 sko"M the character of the 

 tunnels made by the borers. 

 One-hatf natural size. 



