THE TRA CREATION OF WINGS 



35 



The basal connections of the wing trachece of a corisid nymph, Order 

 Hemiptera. — The two tracheal stems to the wings (Fig. 23, c-r and cu-a) 

 have retained their typical relationships in this form, but the cubito-anal 

 trachea {cii-a) to the hind wing is so small at its base that it is followed with 

 difficulty. The anterior and posterior stems of the leg tracheae {as and ps) 

 have attained an almost horizontal position, giving the leg tracheae a 

 T-shape. However, the relationships between the wing and leg tracheae 

 have remained typical. 



TJie basal connections of the wing trachea of a Lcihoceriis nymph, Order 

 Hemiptera. — The tracheae leading to the wings are, of themselves, rather 

 typical save for the divergence of the costal trachea (Fig. 24, c) from the 



Fig. 24. — The basal connections of the wing tracheae of 

 Lethocertis. Side view. 



costo-radial trachea {c-r) of the front wing. The relationships of the leg 

 and wing tracheae at first seem quite puzzling but if conditions are com- 

 pared with those found in notonectids and corisids the explanation seems 

 rather simple. It is quite evident that a "T" shaped trachea similar to 

 that found in the corisid nymph has been modified by the posterior migra- 

 tion of the main trunk to the leg which has resulted in the lengthening of 

 the anterior stem {as) and shortening of the posterior stem {ps) which 

 results in the practical obliteration of the latter. 



The horizontal trunk leading from the mesothoracic spiracle {spi) to the 

 metathoracic spiracle {sp-i) is, therefore, the anterior stem of the leg trachea 

 {as) and the posterior stem of the leg trachea has disappeared. The costo- 

 radial trachea {c-r) has its typical origin with the anterior stem of the leg 

 trachea {as) altho it diverges from the latter some distance posterior to the 

 tj^pical position, and the costal trachea {c) has an independent origin. The 



