1920] Crampton — Lines of Descent of Lower Winged Insects 121 



what living insects are the nearest to the ancestral type from which 

 they were derived; but their near relatives, the Isoptera, are inter- 

 mediate between the Mantid-Blattid forms and the insects related 

 to the Plecoptera, such as the Dermaptera and Embiidina, and 

 thus serve to connect the two groups. The Isoptera are in some 

 respects more highly specialized than the Blattida; but in other 

 features they are much nearer the ancestral Plecopteroid type, and 

 might, therefore, be considered as in a sense more "primitive" than 

 the Blattida. The Zoraptera are very close to the Isoptera; but 

 have preserved many characters present in the Plecopteroid group. 

 In fact, they are anatomically intermediate between the Isoptera on 

 the one hand, and the Plecoptera (svich as Leuctra, Capnia, etc.) 

 on the other, as was pointed out in a recent article in the Proceed- 

 ings of the Entomological Society of Washington. (Vol. 22, p. 98). 

 They thus serve to connect the Isoptera with the Plecopteroid 

 group, and the Isoptera in turn serve to connect them with the 

 Mantida and Blattida. Furthermore, the Zoraptera are remark- 

 ably similar to the ancestors of the Psocidse, the Thysanoptera, 

 and the Psyllid Homoptera, and are very suggestive of the forms 

 leading to the Hymenoptera and Neuroptera, so that a study of 

 their anatomical details is of the utmost importance in attempt- 

 ing to determine the paths of evolution of the higher forms. 



The fossil Protorthoptera, the Grylloblattida, Phasmida, and 

 saltatorial Orthoptera, with their immediate relatives, constitute 

 the superorder Panorthoptera, whose lines of descent are repre- 

 sented in Fig. 4. The ovipositor of the female insect is unusually 

 well developed in many members of this group, and many of them 

 exhibit a tendency toward a thickening of the forewings, which 

 are tj^Dically parchment-like in character. The cerci are usually 

 reduced to a single segment (but not in Grylloblatta) and there is a 

 tendency toward a reduction of the number of tarsal segments to 

 four or less, in many members of the group. The males of some of 

 these insects have retained a pair of styli on the posterior margin of 

 the hypandrium (ninth sternite), and the genitalia are for the most 

 part of a peculiar, highly modified tj'pe (excepting Grijlloblatta) . 



Since Handlirsch maintains that the fossil Protorthoptera are 

 very like the ancestors of the insects in question, their line of de- 

 scent is represented as among the lowest of those shown in Fig. 4. 

 Such forms as Grylloblatta and the interesting little Phasmid 



