94 FOSSIL INSECTS OF THE BRITISH COAL MEASURES. 



stages in the life-history of any species. Handlirsch has recorded the occurrence 

 of several egg-cases of Blattoids from the Carboniferous (' Proc U.S. National 

 Museum,' vol. xxix, p. 71G, 1906). Larval forms have been described by 

 Scudder, Handlirsch, Woodward, and especially by Sellards ('Amer. Journ. 

 Sci.' [4], vol. xviii, p. 113, 1904), but in all cases the remains are too incomplete 

 for satisfactory study. 



The Coal Measure Blattoids show unmistakably that the race had a much 

 earlier ancestry, as they depart widely from the Palreodictyopteroid type, and 

 have attained a high degree of specialisation. The eggs were enclosed in capsules 

 (Ootheca) much as in modern cockroaches, and the development was by a 

 progressive metamorphosis, in which the rudimentary wings were formed at 

 a relatively early stage, and increased in complexity of structure and size 

 at successive ecdyses. It would also appear that the rudimentary wings were 

 attached to the thorax by broad bases, and that the formation of an articular 

 jointTwas not developed until the adult stage was reached. The elements of the 

 thorax were as well developed in Coal Measure times as they are to-day, both in 

 structure and function, while the legs, as seen in examples from Comment rv 

 (Allier), France, were long, spiny, or covered with stiff hairs, and well adapted 

 for walking or running. 



The wings display a remarkable diversity of neuration. The fore-wings are 

 invariably modified by the formation of chitin into stout, horny structures, usually 

 termed " tegmina," which served to protect the more delicate membranous hind- 

 wings concealed beneath them. The costa is always marginal. 



The hind-wings are not well known. When found, they are thin, membranous, 

 larger than the tegmina, and folded beneath them. The enlargement of 

 the wing has taken place over the inner half, the costal and radial areas being 

 reduced, and the anal area not marked off from the rest of the wing by a furrow, 

 as is seen in the fore-wings or tegmina. The wide variation in the neuration 

 of the tegmina furnishes the only satisfactory data for classification. Assuming, 

 as we must, that the Blattoids were derived from the Palaeodictyoptera, the 

 simplest form of Blattoid must be that in which the wing-neuration most nearly 

 approximates to the latter type. This principle is the basis of Handlirsch's 

 classification. 



Modification of the wing-membrane for flight in the case of the hind-wings 

 has brought about, or been accompanied by, a narrowing of the costal and 

 radial areas, a reduction in the strength and extent of these veins, and an 

 increased development of the median and cubital areas, coupled with an increased 

 growth of the wing-membrane inwardly. The hind-wing is. therefore, a much 

 more asymmetrical structure than the fore-wing or tegmen. 



The abdomen is broad, somewhat flattened and well-segmented, but no positive 

 evidence is known of an invagination of the terminal segments to carry the 



