LAUSR

Arthropod herbivore assemblages are used to gain insight into questions about evolution, ecology, diversity, and conservation. However, determination at the species level of small arthropods may be challenging risking underestimating diversity. Here we suggest morphometric analyses as a supplementary determination method, and we demonstrate its use for a study of Chaitophorus species collected from Aspen trees ( Populus tremula ). Although sampled as one colony, the aphids represented three species. Rearing the species separately allowed us to get estimates characteristic of the developmental stages from each of the three species for morphometric comparisons. Recursive partitioning (RP) was used to create a decision tree for choice of morphometric parameters that with significance (p < 0.05) could determine the aphids by species and developmental stage; this insight could then be used as a key for determination. Eight of fifteen morphometric traits were selected by RP to be used in the key. Body length was responsible for nine splits and was consequently the more consistent morphometric trait used in the key.