On the Air- Spaces in Flying Animals. 149 



with the silvery sheen much less noticeable ; and in the 

 thoracic dorsum being less brassy pollinose. It is an inter- 

 mediate form between Thomsoni and iter cms ; iroxn. iterans 

 it differs in the front tarsi of female being widened, abdomen 

 more deeply tinged with red, and dorsum of thorax less 

 brassy pollinose. Palpi are slender, filiform, as in both 

 iterans and Thomsoni. 



Three of the above specimens have three bristles on sides 

 of face near orbits, instead of only two. 



Also one female, Rio Ruidoso, 4 miles west of Dowling's 

 Mill, 6600 feet, July 10, on flowers of sumac, Rhus glabra, L. 

 [Wooton). 



23. Echinomyia, sp. 



Two specimens (male and female) of a blackish species, 

 with a stigma-like spot on wings. Taken by Prof. Wootoa 

 on White JMountain, 9000 feet, July 3, on flowers of Helenium 

 Hoopesii, Gray. 



XIV. — The Physiological Importance of the Air-Spaces in 

 Flying Animals. By R. VOX Lendenfeld*. 



It is well known that in the bodies of the majority of insects 

 and birds large spaces filled with air are met with which 

 appear morphologically as local expansions, relatively as 

 appendages of the respiratory organs. They are developed 

 in very different ways in the different species, and are not 

 present in all insects. In general it may be said that in 

 animals capable of strong and sustained flight they are highly 

 developed and spacious, that in bad fliers they attain a lower 

 degree of development or (as in some insects) do not occur at 

 all, and that in all non-flying insects they are entirely 

 wanting. It is thus rendered probable that they are in some 

 way directly or indirectly connected with the flying motion, 

 and are to be regarded physiologically as organs subservient 

 to fligiit. Further, from the very considerable size of these 

 organs, especially in Hymenoptera and many birds, a con- 

 clusion may be drawn as to the great importance which they 

 must possess. 



With reference to these air-spaces three suppositions are 

 possible : — (1) they are exclusively accessory respiratory 



* Translated by E. E. Austen from the ' Biologisches Centralblatt,' 

 XTi. Bd., No. 21 (November 1, 1896), pp. 774-778. 



