Szekessy Vilmos (szerk.): A Magyar Természettudományi Múzeum évkönyve 60. (Budapest 1968)
Farkas, H.: On the systematics of the family Phytoptidae (Acari: Eriophyoidea)
On the Systematics of the Family Phytoptidae (Acari: Eriophyoidae) By H. FARKAS, Budapest Students of zoological systematics endeavour to evolve the classification of their respective group into a so-called "natural system". It is wellnigh a truism that the natural system is a phylogenetical frame of reference for the animal kingdom. However, the development of a perfect natural system encounters unsurmountable difficulties and thus largely remains an ideal, theoretical aim. Research workers have to rest content with the knowledge that the system they fabricated reflects only within the frame of practical possibilities their attempts to attain the "natural system". Of the innumerable obstacles standing in the way of elaborating the natural system I wish to point out now the one which utterly precludes the clarification of phylogenetical relationships on the basis of paleontologieal findings for a significant number of animal groups. And in the case of such animal groups, none avails but an attempt to work out these relationships by a recourse to the morphological, anatomical, ontological, etc. investigation of the recent species. However, these methods allow to draw mere inferences only. And these inferences are very rarely wholly convincing and unequivocal. Thus, for instance, in the case of studies based on morphology there are any numbers of characters to be considered, and in the majority of species primitive and modern features are present in a mixture. The one and the same species might be regarded as primordial with respect to one, and highly developed with respect to another, of its characters. All these considerations apply in essentials also to the superfamily Eriophyoidea. Their generally accepted system has been elaborated largely by the famous Austrian acarologist, ALFRED NALEPA, followed by our best student of the group, H. KEIFER. Quite naturally, their system cannot be regarded as a perfect "natural system", but it evidently reflects the attempts to evolve a natural one. The oldest systematical units appear at the beginning of the system, and the most developed ones at its end . The classification of the Eriophyoids is based in essentials on two morphological characters or group of characteristics, namely, 1. the gradual diminishing of the numbers of setae, and 2. the gradually more complicated; appearance of the abdomen and the céphalothorax. It can hardly be disputed that, in the case of the Eriophyoids at least, a higher number of setae is to be regarded as a more primordial feature, and that, in the groups exhibiting fewer bristles, the reduction of the setae had been enacted in the course of time. It is similarly manifest that a configuration of the abdomen and céphalothorax resembling the larval state to a greater degree represents a more primordial feature. The two characters thus regarded as ancient ones (the great number of setae on the dorsal shield an the simple constitution of the abdomen and the céphalothorax) coexist in numerous species of the family Phytoptidae. It follows that students have for long regarded this family of the Eriophyoids as the earliest one.
