sitil naturally retards or facilitates the easy movements of the grub 

 iu its constant search for fresh roots. For this reason white-grubs 

 an- worse pest in friable tlian in heavy clay soils. 



(8) Temperature (time of year). The length of tliis instar some- 

 Avhat increases, as do the others, during the winter months, though 

 at no time of year do the grub's activities entirely cease as result of 

 cold Aveather. as happens in more northern latitudes. 



(4) The presence of disease in the grul). As previously stated, 

 infection with the Metarrhizinm fungus greatly retards the activity 

 and growth of tlie grul), as does bacterial infection, thus lengthening 

 the duration of the instar. 



(5) Attack by mites, or by other dermal parasites that molest 

 the grub. 



- THE PRE-PUPAL STAGE. 



The so-called pre-pupal stage of white-grubs is the resting period 

 that occurs at the end of the third in.star tiuring which the grub is 

 preparing for pupation. It is characterized by a puckering or gather- 

 ing of the skin, general flahl)iness, and a discoloration or yellowing 

 in color (see Plate III, tig. 8). The larva lies on its back, dormant, 

 in a rounded, oblong cell about 35 to 40 mm. long; the body is much 

 flattened and the caudal end rather sharply bent upward ; the legs 

 are held stififly outward, close together, and display little or no move- 

 ment. There is no molt between the third instar and the pre-pupal 

 stage. 



From two weeks to a month prior to the pre-pupal stage, the 

 grub shows the approach to pupation by its sluggishness, by the l)ody 

 becoming yellow, more opaque, and harder to the toucli, and by a 

 disappearance of the dark stain' at the caudal end of the body result- 

 ing from the earthy excretions matter within. 



From about a dozen observations of reared grubs, the pre-pupal 

 stage varied from four to seven days. There was in each case an 

 added period of about a week to two weeks during which the grub 

 Avas sluggish and did not feed, thus indicating its j'jreparation for 

 the pre-pupa. 



ft 



THE PUPAL STAGE. 



When the pre-pu[)a molts, the ])upa is at Hrst white and mis- 

 shapen; but within twenty-four hours it has assumed its natural 

 shape (see Plate III, fig. !* ; also Plate W . figs. 1 and 2) and sinning 

 yellow-brown color. The pupa lies on its hack in the cell, and the 



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