58 3T}\ Perinfjuey, a Note on the [Aug., 



the western parts. In a letter wliicli I liad the honour to receive from 

 him, Mons. Cornu mentions having also noticed a similar result pro- 

 duced by an excessive drought and heat ; his observations have been 

 ulteriorly confirmed by those of Balbiani. 



It might have been hoped that the extreme heat and dryness of the 

 climate from November to April would have here acted as the low 

 temperature (10° 0.) does in France. 



Unfortunately there is no ground for such a hope. The phylloxera 

 does not activate, and remains extremely active from September to the 

 middle of April, as shown by the observations — up to date — made not 

 only in my conservatory, where, in spite of all precautions the heat 

 is naturally greater — varying from 66° to 106° Fahr., — but also in 

 the fields. 



In extremely compact argillaceous soil, the surface of which is 

 baked, I have sometimes met with insects, somewhat sluggish in com- 

 parison to those at a greater depth, but that was immediately under 

 the surface only, and they were not dormant. (^) 



I had occasion to examine the roots of one of the vines in the con- 

 servatory with a heat of 87° Fahr., and the insects, both near the 

 surface and also at a depth of 24 inches, were equally active ; they 

 were, however, more numerous at that depth, and had sought evi- 

 dently a damper surrounding. 



The effect of the rain}^ season (winter ?) has been, however, very 

 peculiar, and produced a result nearly akin to that of the hibernation 

 in France. 



After the cold and rainy weather experienced in May last year, I 

 was greatly surprised to find the insect in a semi-comatose state ; the 

 body of the gravid female no longer so spheric or pyriform as usual, 

 was not distended with eggs in the majority of cases ; the young were 

 not active, and the insect in its different stages had assumed a leaden 

 hue, was motionless, hut not dead. 



When exposed to a little warmth, both female and 3'oung revived 

 rapidly ; a few hours exposure to artificial heat was suificient, and a 

 female even gave me three eggs the following day. Towards the end 

 of August the phylloxerae in the conservatory had awakened from 

 their stupor, and on the 1 0th of September the roots of the vines were 

 teeming with phylloxera-life. 



The field observations were made at Mowbray, the only place where 

 I could at that time observe the insect in situ. 



From statistics kindly supplied to me by the Meteorological Commis- 

 sion the mean temperature recorded at the Observatory has been in 

 May, 63-1 ; June, 56-9; July, 53-8; August, 55-6; and September, 

 58*5; the lowest minimum being in May, 47-8 ; June, 49 ; July, 44-4 ; 

 August, 47*8 ; and September, 49 '9. Thus the mean temperature of 

 49°, wliich, according to Cornu, causes the phylloxera to hibernate, 

 has not been readied at Mowbray, and the semi-hibernation of the 

 insect observed by mys(4f at the end of May points to a racial predt's- 

 position in the insect, which leads to the supposition t]iat> it lias been 

 in the Colony for a short time, and has not l)een suiiiciontly acclima- 

 tised as yet to be insensible to a period of cold superior to tliat causing 

 a complete hibernation in Europe. As for the greater period of heat, 



f) These conclusions hnve since been strengthened by my observations during 



the wiiitM, for tlie viney in my conservatory. 



