512 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



now referred to three separate genera and I suspect that one or more species 

 bears the alias of still a fourth genus. Distinct races exist within many species 

 of mayflies and in some genera the problem of naming and making known these 

 races and the causative factors of their formation and present distribution is 

 very i:)ressing. This inevitably leads to the problem of obtaining larger samples 

 of specimens, topotypes of older species, and especiall}^ reared series. As repre- 

 sentatives of an ancient group of insects that are, because of their short adult 

 life and tendency to desiccation, seldom dispersed any great distance by air, may- 

 flies are prime subjects for biogeographic studies. For those willing to meet the 

 special problems of collecting and preserving the insects of this order, there is 

 a promising field of research. 



PLECOPTERA 



Per Brinck 

 Lunds Universitets Zoologiska Institution 



The history of our knowledge of the stoneflies is comparatively short. Not 

 until late in the IMiddle Ages are they even modestly mentioned in the literature. 

 Some authors of the sixteenth century dealt with them as grosse Wassermiicken 

 (big water flies). In 1603 in his TheriotropJieum Silesiae Caspar Schwenckfeld 

 described a perla as Biusca caudata. Moufet in 1643 (Insectorum sive Mini- 

 morum Animalium Theatrum), J. Johnston in 1653 [Historia Naturalis de In- 

 sectis, Libri III), and J. Wagner in 1680 {Historia Naturalis Helvetiae Curiosa) 

 describe a Musca aquatilis aestiva major which is also a perla. In the litera- 

 ture of the eighteenth century, stoneflies were mentioned more often, but they 

 had no name of their own until much later. 



It is true that Perla, a name which has long been applied to a genus of well- 

 known European stoneflies, appeared as early as 1602 in Aldrovandi's De Ani- 

 7nalihus Insectis Libri VII. But it did not refer to a stonefly, for at that time 

 perla was the common name for dragonflies, the larvae of which were known as 

 Libella fluviatilis. Moufet (oj). cit.) recognized the association between the lar- 

 vae and the imagines and restricted the name Libella to Odonata. For some time 

 Libella and Perla were used side by side (cf. Goedaert: Historia Insectorum 

 Generalis, several editions), but in the eighteenth century we meet with Libella 

 only. Pei'la disappeared as a generic name until it was revived by E. L. Geoffroy 

 in 1762 {Histoire abregee des insectes) and by Cuvier (1798), and P. A. La- 

 treille (1802) made it the type of a section or family Perlariae among the 

 Neuroptera. 



Stoneflies were figured early. There is an excellent illustration of a perla in 

 G. Hoefnagel's Archetypa Studiaque (1592) and Diversae Insectorum vola- 

 tiliwn (1630). No text accompanies the figures. 



The number of pre-Linnaean species of Plecoptera is very small and they 

 cannot be identified with any certainty. Linnaeus and his pupils and the Lin- 



