Project: 1998-05. Report - Multiple-Entry Key Aphids on Forest Trees in New Zealand
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Date: 1999 Author: D. A. J. Teulon Publication: Crop and Food Research Confidential Report No. 619 Project reference: 1998-05 Full report is available from: |
Executive summary:
Abstract
A multiple entry key for wingless and winged aphids (Homoptera: Aphididae) on New Zealand forest trees is described. Approximately 25 aphid species found on economically important forest trees as well as at least 30 species not found in New Zealand, but considered to be of quarantine importance, are included. Simple key characters in discriminating matrices are used for aphid identification.
Introduction
About 120 aphid species have been recorded in New Zealand (VFE, unpublished data). The vast majority of these are considered to be introductions and many are pests of economic importance including a number on forest trees. There are many different reasons for the need to accurately identify an organism. For species in New Zealand of economic importance this includes the need to find pertinent literature regarding basic information and/or appropriate control measures. New aphid species found on New Zealandīs borders need to be identified quickly so that appropriate actions can be taken to minimise their impact. A full taxonomic work on the aphids of New Zealand featuring a detailed dichotomous key to all species, including the species of economic importance, is soon to be completed (VFE, unpublished manuscript). However, in many instances such keys become overly complex and a more simple approach is worthwhile.
The multiple entry key that follows is an attempt to simplify the identification of wingless and winged adult aphids of economic importance to forest trees in New Zealand and is designed to be used by economic entomologists, students of entomology and other non-specialist taxonomists.
Methods
Structure. The multi-entry keys for forest tree aphids are grouped according to closely related tree species (usually genera). Separate discriminating matrices (see below) are given for wingless and winged aphids recorded in New Zealand as well as wingless aphids considered to be of quarantine significance and not recorded in New Zealand (see below).
The key is for adult aphids only. It is, therefore, important to ensure that specimens to be identified are adults. The presence of a distinct cauda is usually the most convenient way of picking out the wingless adults in a sample containing both immature and adults aphids. The presence of an anal plate is another useful character to distinguish adult from immature aphids. Winged aphids are all adults.
For all aphids listed in each matrix a set of nine key characters is given which are characteristic for each species (see below). A number of extra characteristic features are also listed to enhance accurate identification. Aphids can be identified by matching the appropriate descriptions found in the matrices with those of the specimen to be identified. Illustrations are provided for species found within New Zealand.
Key characters. Nine key characters are listed in each discriminating matrix. These include: (1) the shape of the frons, (2) dorsal pigmentation, (3) the number of rhinaria on the antennal segments (especially segment 111 for wingless aphids), (4) the ratio between the terminal process and the base of the last antennal segment, (5) the shape and (6) colour of the siphunculi, and (7) the shape and (8) colour and (9) number of hairs on the cauda. Full descriptions and illustrations of key characters are given on pages 3-8.
Key characters were selected to give the greatest possible discrimination between species, to be simple to understand and learn, and to be easily recognised with a good binocular microscope. In most cases the nine key characters are sufficient for the identification of all species found on a given host tree (or group of host trees). A number of other features are also listed for each species. These features may be useful to confirm identification and can be used where the nine characters fail to differentiate between species completely.
Species included. For each tree (or group of closely related trees) all aphid species recorded in New Zealand with known host associations with that tree are included in the discriminating matrix. Host plant associations were based on Blackman and Eastop (1994). A separate key is provided to polyphagous aphid species that may be found on a number of trees from time to time.
A selection of wingless aphid species of economic importance not found in New Zealand is included in separate matrices. For clarity, these species are bolded in the discriminating matrices. Criteria for selecting aphid species for these matrices included their present distribution and economic status, the likelihood of them causing economic damage in New Zealand, and their present rate of movement throughout the world. In some cases only genera are included in these keys as a full list would become too large. Furthermore, in some cases some of these aphids cannot be identified with adult forms. A list of aphids with a lower economic status and/or potential risk of entering New Zealand is also included. Aphids from these lists can be further identified using the keys found in Blackman and Eastop (1994).
Corrections. This is an early attempt to develop a multiple entry key for New Zealand aphids on forest trees and there are probably a number of inconsistencies and inaccuracies. The author would appreciate any feedback concerning the use and accuracy of the key so that further improvements can be made.
Full report is available from:
Crop & Food Research
Private bag 4704
Christchurch
New Zealand
