16 
WORK IN EUROPE 
Meloidae (among tlie Coleoptera), Mantispa (among the Neuroptera), 
Gyrtidae , Conopidae, Pipunculidae , Oestridae, Tacliinidae, Plioridae , 
even Anthrax, Bombylius , and others (among the Diptera), and 
numerous similar instances among the Hymenoptera exist. Com¬ 
mensalism likewise produces aberrant forms, like the Pselaphidae , 
Paussidae, and Lomechusa strumosa ( Staphylinidae ) among the 
Coleoptera, and it is difficult to draw the line between commensalism 
and some forms of parasitism in the widest acceptation of the term. 
In the course of my new studies I came gradually to abandon 
descriptive dipterology. Since 1890 especially, I undertook a more 
thorough study of the earlier literature, which has been much 
neglected by most authors. I found that valuable hints contained 
in the writings of Latreille , Lyonet , Rob.-Desvoidy , etc., had been 
overlooked or insufficiently studied, and that, by means of a study 
of earlier authors, neglected characters introduced by them might 
be rediscovered, and the synonymy of genera and species, the sys¬ 
tematic nomenclature, and the terminology of organs might be 
improved. Thus a series of papers, classificatory, critical, historical, 
and bibliographical, came to be published. 
These papers either bore a general character, like that already 
quoted: On the Characters of the three Divisions , etc., 130 (1892) ; or 
they treated of single families and groups, like the Blepharoceridae , 
60 (18T8), 124 (1891), 144 (1895); Psychodidae , 146 (1895), 150 
(1895); Nemestrinidae , 162 (1897); Apiocerina, 93 (1883), 109 
(1886), 123 (1891). A similar paper on Cyrtidae, which was nearly 
finished in 1895, is still unpublished. The much-debated question 
on the right spelling of My das or Midas was critically settled, 149 
(1895). Similar questions on the terminology of certain organs 
were historically investigated in the papers: On the Terms Teyula , 
Squama, Alula, etc., 154 (1896); On the Terms Calyptrata and Acalyp- 
trata , 157 (1897); Zur Greschichte der sogenannten Brustyrdte , etc., 
135 (1893). Criticisms appeared of publications of contemporary 
authors, Brauer , 89 (1882), 136 (1893), 137 (1893) ; Mik, 122 (1890), 
126 (1891), 156 (1897); Williston , 127 (1891); also bibliographical 
papers, like the Lists of the publications of Rondani , 79 (1881), 98 
(1884), 106 (1885) ; and Loew , 104 (1884) ; a critical appreciation 
of the relative value of the two editions of Loew's “ Tosener Dip- 
