6 FOSSIL INSECTS OF THE BRITISH COAL MEASURES. 



valuable information is supplied by the deposits, or by the nature of the associated 

 forms of life. 



The great group of the Palseodictyoptera and certain of the Protorthoptera 

 and Protodonata had large wings, and Avere powerful fliers. We should therefore 

 expect to find their remains widely dispersed in deposits of varied nature. This 

 seems to be the case. Compact heavy-bodied insects like the Blattoids would have 

 a more limited range, and their bodies after death could not be carried to great 

 distances. Larval forms would in most cases be included in the deposits in the 

 immediate neighbourhood of the area in which they lived. 



M. Henri Fayol, in his description of the Coal Measures of Coinmentry, 

 France, shows that these deposits were laid down in narrow land-locked lakes of a 

 trough-like form lying in depressions of older schistose and crystalline rocks. 

 The tranquil waters received only the finest mud in suspension, and the resultant 

 inudstones have yielded a large insect-fauna, in which Blattoids are most numerous. 

 The bodies of the insects are preserved in many cases. Certain of the insects were 

 strong fliers, and their occurrence with the bodies intact indicates that they, in 

 all probability, haunted the vicinity of the lakes and flew over them. When 

 strongly-flying insects like Boltonites radstockensis or Litliosialis brongniarti died 

 upon the land, the wings, because of their membranous and chitinous nature, 

 would persist after the destruction of the softer body, and be swept off into streams 

 after heavy rains or flooding of the land-surface, their great superficial area 

 combined with their lightness making flotation easy. 



The transference of insect-wings from the land into water would be accom- 

 panied by the drifting of plant-material, and the two would be buried together in 

 the deposit then forming. The wing of Boltonites from Radstock was found with 

 plant-remains in deposits of this sort, and may be taken as a proof, supported as 

 it is by other examples of Protodonate wings, that these insects lived over the 

 land and died upon it. 



The Palseodictyoptera, with their wings capable only of an up-and-down move- 

 ment in one plane at right-angles to the body, and, when in a position of rest, 

 disposed straight outwards, are not likely to have frequented the ground, except 

 in the open. These insects, like most of the Palaeozoic forms, were all of large size, 

 as contrasted with living types. Pruvost assumes that the characters of the wing 

 unfitted these insects for a forest life, and that they must have been restricted to 

 flight in the open neighbourhood of swamp pools. I do not wholly agree with 

 this assumption, for the branches and leaves of the Coal Measure plants do not 

 seem to have had so great a density and interlacing of foliage as seriously to 

 impede the flight of powerful winged insects. There seems no reason why these 

 insects should not have lived among the brakes of Lepidodendroid and Calamitean 

 trees, and after death fallen or been blown into adjacent waters. The fact that 

 isolated wings are often found in perfect condition and without any signs of wear 



