74 Eighteenth Report State Entomologist of Minnesota — 1920 



genus. Such types are important in settling questions of i)rior!ly. or 

 the status of the genus as used differently hy various authors. Impor- 

 tant as such types are, at least in the present stage of taxonomy, the 

 chronological type is really the least important of the three, and will 

 in due time largely be replaced by the second and used only in its strict 

 historical sense. The phylogenetic type is the real type of the genus. 

 Such types can not be set arbitrarily, and can be recognized only by 

 an extended study of all the species of a genus. It is the species that 

 carries all the generic characters in fullest development. As types 

 like this can not be set without taking into consideration all the species 

 of the genus, the monographer of the future, it is hoped, will set such 

 types for the genera which will be the real phylogenetic types, replacing, 

 at least in many cases, the chronological type which is often far from 

 typical, being more often an extreme form that happened to be first 

 described or set as type. The older entomologists often spoke about 

 typical species, vaguely to be sure as was necessary with the incom- 

 plete knowledge of the family in their time. At present we rarely find 

 this idea expressed, and the only type worth considering seems to be 

 the chronological type leading more and more to an artificial tax- 

 onomy, and not to the true phylogenetic as we find it in nature. The 

 biological type is better known and recognized, but we too often speak 

 and write as if it was already in our possession, which is far from 

 the case. Each species is potentially a biological type, or eventually 

 will become one. Too many of our species are only partial or frag- 

 mentary types based on a single form, usually the migrant, and ex- 

 pressed by a few apparent differences. The biological type in the 

 family Aphididae is a very complex thing not easily ascertained or 

 grasped. It includes in mo.st cases at least five or six distinct forms, 

 the fundatrix, spuria, migrant, and male and female, of which the 

 one is no more important than the other, but all must be considered 

 and fused into a whole, the biological species or type. Much good 

 work has been done of late in this direction, but much more remains 

 to be done before we can safely begin to settle the final status of the 

 various categories. 



The taxonomy of the Aphididae is a fascinating subject and has 

 attracted an unusually large number of devotees for a century or more, 

 some of a very high order of mind. It is a field not safe for the 

 novice to enter with impunity, as many of the best, w^ho spent a good 

 part of their lifework in the field, still considered themselves as nov- 

 ices, and felt their way with caution, trying to grasp the outline and 

 some faint idea of the grandeur of the phylogenetic conception of the 



