58 Psyche [June 



Explanation of Plate I. 



Fig, 1. Diagrammatic figure of the posterior respiratory organ 

 of a dipterous larva indicating the several diagnostic characters. 

 * Diameter of circular plate. 1, 2, 3, 4, first, second, third and 

 fourth interspiracular spaces of left stigmal plate. I, II, III, 

 dorsal, median and ventral slit-like spiracles, respectively, of right 

 stigmal plate. IV, the left circular plate or "button." 



Fig. 2. The micro-protractor showing arrangement of ruled 

 angles. The various possible combinations from 5° to 360° indi- 

 cated by the concentric lines. 



A PHYLOGENETIC STUDY OF THE MESOTHORACIC 

 TERGA AND WING BASES IN HYMENOPTERA, 

 NEUROPTERA, MECOPTERA, DIPTERA, TRICHOP- 

 TERA AND LEPIDOPTERA.^ 



By G. C. Crampton, Ph.D. 



In several papers dealing with the phylogeny of insects, the 

 Hymenoptera, Neuroptera, Mecoptera, Diptera, Siphonaptera, 

 Trichoptera, Lepidoptera and their allies were grouped in a super- 

 order called the '' Panneuroptera." A portion of the evidence for 

 such a grouping, based upon the study of the genitalia of males, 

 has already been presented in Psyche, Vol. 25, p. 47, and in 

 the Proc. Ent. Soc. Washington, Vol. 21; and in the present 

 paper, I would briefly review the evidences of relationships indi- 

 cated by the nature of the mesothoracic terga and wing bases in 

 these insects. The terminology here adopted is that previously 

 applied to the terga and wing bases of the Embiidse, Plecoptera, 

 Coleoptera and Dermaptera (Psyche, Vol. 25, p. 4), the Blattidse, 

 Plecoptera and Neuroptera (Jour. N. Y. Ent. Soc, Vol. 24, p. 1), 

 the Orthoptera (Ann. Ent. Soc. America, Vol. 11, p. 347), and the 

 Hymenoptera and Diptera (Jour. N. Y. Ent. Soc, Vol. 22, p. 248). 



In the lower insects, the metathorax is subequal in size to the 

 mesothorax, and in a few instances is even larger than the meso- 

 thorax. In the insects here considered, however, the mesothorax 

 is usually the larger of the two, and since the metathorax becomes 



' Contribution from the Entomological Laboratory of the Massachusetts Agricultural 

 College, Amherst, Mass. 



