CONDITIONS OF LARVAL INSECT LIFE. 7 



and tear such as the wings of aged insects show to-day, raises the question whether 

 in some cases the wings were not shed, as in certain species of recent ants, the 

 shorn insect continuing its life as a ground-feeder. 



The Protorthoptera Avere, judging from the structure of their mouth-parts, 

 somewhat general feeders or carnivorous, and the presence of strong walking legs 

 suggests that they spent much of their life on the ground, possibly along the 

 margins of swamps, where food would be especially abundant. They had, never- 

 theless, powerful wings, and some members, such as the (Edischiidae, had legs 

 adapted for leaping. Ortlioptera, represented chiefly by Blattoid forms, were all 

 fitted for flight by means of their large membranous hind-wings, and equally well 

 fitted by powerful walking legs for life on the ground. In repose the hind- 

 wings were hidden under the modified fore-wings. 



I have elsewhere given my reason for a belief that the Blattoids were not 

 wholly phytophagous, but in all probability carnivorous also (' Quart. Journ. Geol. 

 Soc.,' vol. Ixvii, p. 153, 1911). 



Blattoids may also have entered the water in search of food, for the hind 

 flying wings would be securely protected by the tegmina, whose broad muscular 

 bases of attachment were sufficiently powerful to compress them down on the back 

 and prevent water entering beneath, just as in the case of the living water-beetle, 

 Hydrophilus piceus. The chitinous surface of the body and of the tegmina would 

 not hinder progress in water, for their surfaces are no rougher than those of the 

 modern Dytiscus, nor would the insect on emerging bring with it so heavy a film 

 of water as to clog its movements. An objection may be found in the presence of 

 stout bristle-like hairs on the legs seen on such forms as Necymylacris lerickei 

 (Bolton) (1917, 'Mem. and Proc. Lit. and Phil. Soc. Manchester,' vol. Ixi, p. 15), 

 which might conceivably cause air-bubbles to cling in such profusion as to prevent 

 the insect being able to submerge. The presence of fine hairs on the swimming 

 legs of Hydrophiliis and Dijtiscus does not hinder the immersion of these insects in 

 water, so that this is not a valid objection. If no hindrance to immersion was 

 caused by the bristle-like hairs, they may have been useful in assisting the act of 

 swimming. 



I think the probabilities are in favour of the Blattoids being at least semi- 

 aquatic as well as land insects. 



CONDITIONS OF LARVAL INSECT LIFE. 



The conditions under which larval life was passed are even more conjectural. 

 The Protodonata may be regarded as insects whose larvae must have been aquatic, 

 like the aquatic larvae of the Odonata now living, but Tillyard (1917, ' The Biology 

 of Dragonflies,' Camb. Univ. Press, p. 306) conjectures that since adult Prot- 

 odonata are found at Commentry without the occurrence of larval forms, the latter 



