A PHYLOGENETIC STUDY OF THE LARVAL AND ADULT 



HEAD IN NEUROPTERA, MECOPTERA, DIPTERA, 



AND TRICHOPTERA.* 



By G. C. Crampton, Ph. D. 



Since practically all of the recent attempts to trace the 

 phylogeny of insects have been based upon the study of the 

 wing veins, which are extremely variable features within the 

 same order, or even family, of insects, it has seemed advisable 

 to examine other less variable structures, and those from widely 

 different parts of the body, in order to ascertain if such a study 

 would confirm or disprove the conclusions reached from a 

 study of the wing veins alone. The present paper is therefore 

 offered as one of a series in which the various structures which 

 appear to be the most useful for a phylogenetic study, have 

 been compared in the Neuroptera, Mecoptera, Diptera and 

 Trichoptera. Many of the accompanying rough sketches 

 were made from material kindly loaned to me by Dr. N. K. 

 Banks, to whom I am deeply indebted for many valuable 

 suggestions, and for the privilege of examining the specimens 

 in his unusually extensive collection of Neuroptera, Mecoptera, 

 and Trichoptera. I am also greatly indebted to Dr. C. W. 

 Johnson for the identification of the Diptera used in the prepara- 

 tion of this paper. 



It is customary to speak of this or that single type as the an- 

 cestral one for a large group of insects, but I think that this is a mis- 

 taken conception, since a study of the ancestral groups (or rather, 

 those which have departed but little from the condition char- 

 acteristic of the ancestors of other insects) would indicate that 

 the ancestral forms frequently differed quite markedly among 

 themselves, exhibiting several developmental tendencies (instead 

 of merely one type) which frequently manifest themselves in 

 the evolutionary series of the forms derived from them. As an 

 illustration of this view, I would call attention to the "short- 

 headed" series of Neuroptera, Mecoptera, and Diptera shown 

 in Figures 1, 2 and 3, and the "long-headed" series of the 

 same groups of insects shown in Figures 4, 5 and 6. These 



*Contribution from the Entomological Laboratory of the Massachusetts 

 Agricultural College, Amherst, Mass. 



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