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CHAPTER lI.—RESEARCH AND EXPERIMENTS. 1. Eorest Entomology. General. As mentioned in last year's report, forest entomological-research work is now being carried out at the Cawthron Institute, Nelson, under the direction of Dr. David Miller, assisted by the Forest Service Entomologist. The latter was seconded for duty to the Forest Biological Research Station, Cawthron Institute, as from the Ist January, 1930, and took with him the necessary Service equipment. The Institute insectaries have been placed at his disposal where necessary, pending the erection of those to be used solely for forestry investigations. Researches. Good progress with a wide programme of researches has been made and the results obtained jvere very satisfactory. In view of the large afforestation schemes now being developed in the Dominion, the investigations have been confined mainly into the insect pests of exotic timber-trees. Minor routine studies of matters affecting the indigenous timbers have, however, received attention, and preparations have been made to further extend this line of research during the coming year to embrace the more outstanding problems connected with the growth and utilization of the native timbers. Insect Survey. The insect survey has as its object the collection of data upon the distribution and degree of infestation of insects affecting exotic timber-trees. Of necessity as much matter concerning site factors, growth, and the silvical treatment of the various stands must be procured at the same time ; in fact, while the prevalence and degree of damage caused by insect pests is measured, all the factors which enable the conditions so measured to obtain must be noted and weighed. The survey has been extended this year to the Auckland and Rotorua Regions. While much valuable data were obtained the field work undertaken in Rotorua Region is only considered to be a preliminary reconnaisance in preparation for more intensive work next year. To facilitate this further work the establishment of a permanent field station has been decided upon. The survey is considered to be a vitally important part of the researches, the results determining to a large extent the particular pests upon which investigations shall be carried out. Sirex juvencus.—The control of Sirexjuvencus by use of the ichneumonid parasite Rhyssa persuasoria has been undertaken. Consignments of this insect have been received from Farnharn Royal, and from these adults have been successfully reared. No difficulty was encountered with mating, and a distribution of the parasite to infested stands at Hanmer Springs, Dumgree, and Blenheim, in the South Island, and at Palmerston North in the North Island, has been made. It is yet too early to state definitely whether the insect has become established, but observations made at the time of liberation are most encouraging, oviposition upon infested trees being observed. While the biology of Sirex is known generally, more intensive studies into the question are being prosecuted in view of the arrival in the near future of a further parasite from Europe. On all occasions the improvement of the silvicultural conditions of the infested stands has been urged. Neomyzaphis abietina. —-The spruce aphis attacks members of the genus Picea in New Zealand, and is particularly severe in the case of P. excelsa and P. sitchensis. These two trees are subject to repeated defoliation and are rdtimately killed. Studies have been carried out upon the biology of the insect, and one complete generation has been followed through. The occurrence of allate forms and the question of migration is receiving close attention, the possibility of the insect alternating with some plant outside the genus Picea is a most important one. Records of past fluctuations in the degree of infestation have been searched, and attempts to correlate ecological factors with these have been but partially successful, the paucity of reliable date proving a considerable handicap. A Hemerobid parasite of the spruce aphis has been discovered in New Zealand, but its occurrence has been ascertained to be too slight to have any marked controlling influence upon the pest. The aphis does not attack the spring foliage of the spruce, but the advent of the conifer spinning mite, which does attack this foliage, has made a complication in the investigation which has consequently been extended to include the mite. Inquiries for suitable parasites of N. abietina have been made, and it is hoped that such an insect will reach the Dominion next year. The investigation into the insect enemies of spruce is one of the station's most important activities, as it is well known that spruce is a valuable tree for the production of paper pulp. Hylastes ater. —The initial outbreak of this insect which occurred at Foxton was recorded in July. The insect was quickly identified and a survey made to ascertain the extent of the infestation with a view to putting into force measures for the total eradication of the pest. Unfortunately it was found to be firmly established over an area too large in size for such measures to be attempted. The insect develops in the stumps and roots of pines and in the adult stage attacks young conifers. The lifehistory of the insect has been worked out, and plans for its control by means of trap stems formulated. Sample plots have been placed in the infested area and careful records are being kept of the actual loss which this insect is causing. Eucalypt-pests. —The research.into the pests of eucalyptus concerned two insects.