Preliminary Note on the Structure of the Pretarsus and its Possible Phylogenetic Significance

The uncertain reliability of morphological structures for determining ancestral relations is well known and the extreme care and attention to the vagaries of parallelism, specialization, etc. so necessary for the development of valid theories have been rightly emphasized of recent years. However, in spite of its late disrepute, there is yet much to be learned from comparative morphology if sufficiently long series are studied and checked with the trends of parallel structures and if a most judicious interpretation of the evidenoe is demanded. The primary purpose of this paper is to indicate the type of claw-segment found in the important insectan orders together with the common basic plan occurring throughout and also to outline possible homologies which further study and examination of selected and thoroughly representative series from each order may support. Although i t is impossible a t the present stage to offer any evidence substantial enough to warrant forming exact conclusions as to homologies from order to order, to. say .nothing of attempting to solve phylogenetic problems, there are without doubt most significant agreements in many cases which provide definite possibilities to be tested by further study. Especially important are those correlations which fall in with phylogenetic concepts already accepted (or debated) from the evidence of the comparative morphology of other structures.