THE MOUTH-PARTS OF PANGONIA LONGIROSTRIS. 265 



"those in the female are firmly attached to the endo-skeleton of the head and are 

 hairy over a portion of their length only, the apices being naked and armed with 

 strong teeth. , 



(3) The labrum-epipharynx of the male has a weak chitinised apex and is hairy ; 

 in the female it has a firm apex, strengthened by a median band of chitin, and is 

 armed with strong teeth and not hairy. 



(4) The hypopharvnx of the male differs from that of the female only in being 

 broader at the apex. 



(5) The labium is similar in the two sexes, and the pseudotracheal teeth are found 

 in both male and female. 



I conclude from these observations that the male could only suck blood which 

 was flowing from a wound already present on an animal, such as might be caused 

 by the bite of a female Tabanid. I mention this as a possibility, but do not think 

 it is at all likely to occur, as I have been unable to find any reference to a male 

 Tabanid sucking blood. They are always found sucking up the nectar of flowers. 



The female is quite competent to suck blood, but can at any time suck up also 

 the juices of flowers through her proboscis. 



The most natural way in which the former process would be carried out seems to 

 me to be the third of the three different methods I have enumerated above on 

 p. 257. The female alights, punctures with her stylets and then sucks up blood 

 through the proboscis, either while settled or on the wing. It is possible, however, 

 that certain species feed only while hovering and others only when settled on the 

 skin, but further observations are greatly needed. 



The idea that Pangonia longirostris could pierce the skin with its proboscis seems 

 to me quite untenable, as the apex of this organ is not pointed and could only be 

 thrust into anything by the close apposition of the two labella. In this case, all 

 possible value that the pseudotracheal teeth might have as piercing organs would 

 be lost, seeing that they would be enclosed inside the labella. There are, too, some 

 short but rather stout spines projecting outwards from the outer edge of the labella, 

 which would hinder any attempt to thrust in the proboscis. As pseudotracheal 

 teeth are found on the labella of such a purely flower-haunting family as the 

 Bombyliidae, and as they are also present in the male P. longirostris, I do not 

 consider that their presence has any significance in deciding whether an insect is a 

 blood-sucker or not. According to Dimmock (4) the Bombyliidae use these teeth 

 to scratch the surface of flowers, and no doubt their presence in Pangonia can be 

 explained in the same way. 



Dr. Imms states that in the living insect the apex of the proboscis is flexible and 

 has not the rigidity usually associated with piercing organs. 



YI. Comparison of the Mouth-parts with those of other Tabanidae. 



The other Tabanidae with which Pangonia longirostris will be compared are 

 species of Tabanus, Chrysops, Haematopota, and other species of Pangonia. The 

 only literature that I have found which deals with the mouth-parts of the males of 

 this family are the writings of Hansen (7), Meinert (10), both of whom give figures 

 of various Tabanidae, and Wesche (18), who gives a figure of a male Pangonia 



