10 ILLINOIS BIOLOGICAL MONOGRAPHS [328 



(1893). This system of classification is adopted in principle in the present 

 paper, for the writer believes that by judicious discrimination between the 

 palingenetic and the cenogenetic peculiarities, the characters manifested 

 by immature insects may be interpreted as indicating the genetic affinities 

 of the insects under consideration, and that in this sense the immature 

 stages of insects are of systematic importance. A classification based upon 

 such larval characters should agree in essential points with that based 

 upon the adult characters chosen for their phylogenetic value, and there- 

 fore it is interesting to see whether MacGillivray's alary system is justified 

 by a study of the larvae. It must be stated here that Dr. MacGillivray 

 does not accept all my conclusions as to the relation of the families based 

 upon a study of the larvae. 



The immature stages of the Tenthredinoidea of more common occur- 

 rence seem to have attracted the attention of naturalists from an early 

 time. In Moufet's Theatorum Insectorum (1634) the adult saw-flies 

 are referred to the group "Vespa" and what seems to be a Tremex to 

 "Odonata," but no mention of the larvae is made. Goedart (1682) was 

 the first naturalist to make observations on the larvae of a saw-fly. His 

 records, rendered in interesting archaic terms, clearly indicate that he had 

 under observation the larvae of Cimbex or Trichiosoma on Salix, and Arge 

 on Rosa. Madame Merian (1730) pictured saw-fly larvae together with 

 those of the Lepidoptera, as may be seen on her plates 22, 25, and H. 

 Swammerdamm's (1737) figure 1, table XLIV, refers to galls on the 

 leaves and stems of Salix apparently made by Pontania or Euura. He 

 also figured a larva having fifteen segments with larvapods on abdominal 

 segments 3-8 and 11. Frisch (1766) figured about seven species and 

 recorded observations on their life-history. De Geer, as cited by Bergmann, 

 on the authority of Le Peletier (1823), had seen a larva with twenty- 

 two feet exclusive of the anal larvapods. According to the same authority, 

 Reaumur observed certain larvae with twenty-four feet, indicating a 

 xyelidan condition. Linnaeus (1758) recorded the food-plants of twenty- 

 two species of saw-flies out of the forty species of "Tenthredo" enumer- 

 ated, and spoke of the larvae in general of "Tenthredonis larvae pleraeque 

 folia plantarum exedunt, polypodae, seu pedibus plus quam XVI com- 

 muniter instructae," Following Linnaeus many students of the Tenthre- 

 dinoidea contributed much to a knowledge of the immature stages, altho 

 quite disproportionately to their larger contributions to that of the adults. 

 Among those who have done much towards the progress of our knowledge 

 of the larvae, either as original investigators or as compilers or as both, 

 the following are the more important: Andre, Brischke, Cameron, Costa, 

 Dahlbom, Dalla Torre, Dufour, Dyar, Fallen, Hartig, Kaltenbach, Kirby, 

 Klug, Konow, Latreille, Leach, Middleton, Newman, Oliver, Panzer, 

 Le Peletier, Snellen von Vollenhoven, Spinola, Westwood, and Zaddach. 



