THE MOUTH-PARTS OF PANGONIA LONGIROSTRIS. 255 



to be found a series beginning with those types that have a proboscis that hardly 

 extends beyond the head, and ending with Pangonia longirostris in which it extends 

 to a distance greatly exceeding the length of the body. The precise economic 

 importance of the family Tabanidae seems to be doubtful at present. Austen (2) 

 in 1909 says that it has not been proved or even seriously suggested that any 

 species of Pangonia is the regular transmitter of any micro-organism pathogenic 

 to animals or man. According to Fantham, Stephens and Theobald (5) in 1916, 

 Martoglio says that the trypanosome disease of dromedaries known as salaf is 

 " transmitted " by Tabanidae, especially Pangonia magrettii and P. beckeri, in 

 Italian Somaliland. 



In addition to this, the same three authors state that Haematopota can carry 

 Trypanosoma evansi (causing surra in horses) and that Ghrysops conveys Filaria loa 

 in Southern Nigeria, and in Algeria Dr. E. Sergent has proved that a species of 

 Tabanus can transmit three forms of animal trypanosomiasis.* From this it is 

 evident that the Tabanidae are of importance from an economic view, and further 

 investigation may show this importance to be greater than has been demonstrated 

 at present. It is one of the characteristics of the family to which Pangonia belongs 

 that the males are without mandibles, and do not feed on blood to anything 

 approaching the same extent that the females do ; they seem to feed chiefly on the 

 nectar of flowers. In the genus Pangonia are many species with a very long 

 proboscis, and Lutz (quoted by Austen) thinks that this points to a liquid diet other 

 than blood. From his own observations Lutz doubts whether species in which such 

 an organ exists bite and suck blood on the wing. This agrees with the view of 

 Mr. LI. Lloyd who writes that " the long proboscis in the Pangoninae is used to 

 extract the nectar from flowers which they do while hovering, much in the manner 

 of many Sphingid moths." The experience of Dr. Imms in India with Pangonia 

 longirostris is that they are found on the borders of forests towards the end of the 

 rainy season, feeding on flowers of the orders Scrophulariaceae and Labiatae by 

 thrusting their proboscis into them, poising themselves in the air during the process. 

 He has never seen them attacking man or cattle, and in an experiment which he 

 carried out by enclosing his arm in a loose gauze sleeve containing a female of this 

 species, he found that the insect showed no inclination to use its mouth-parts. 

 This experiment, Dr. Imms informs me, cannot be regarded as conclusive, as the 

 insect had not full freedom for hovering on the wing. 



Various species of Pangonia have been found attacking man or cattle in different 

 parts of the world, and their methods of attack differ considerably in the experience 

 of the observers. This fact appears to me to be natural owing to the variation in 

 the relative lengths of the labium and the other trophi. 



Westermann [quoted both by Westwood (20) and Austen (2)] found Pangonia 

 rostrata a very troublesome species to domestic animals at the Cape, but says that 

 this species seems to prefer the flowers of Pelargonium. He held the view that, 

 owing to the length of the proboscis, it can bite only when on the wing. In the 

 opinion of Westwood (20) P. longirostris could not use its lancets, except by 



* [M. B. Mitzmain has demonstrated the transmission of surra by Tabanus striatus, F., 

 in the Philippines. — Ed.] 



