1913] Kershaw — The Alimentary Canal of Flata an I other Homoptera 179 



move endways or disintegrate, passing through the recently- 

 secreted membranes to the rectum, the recent membranes merely 

 being pushed inwards (towards the centre of the canal) by yet 

 more recent membranes. 



The reservoir epithelium, tested by litmus in many specimens, 

 invariably gave a very decidedly acid reaction; but the juices of 

 leaves and young stems of Eucalyptus robusta, on which the 

 Flatids were feeding, is very acid and immediately reddens blue 

 litmus paper. Probably, therefore, the acidity of the reservoir 

 is due to the food. From the results of feeding several Siphanta 

 on rods of pith soaking in red or acid azolitmin, the secretions of 

 the whole alimentary canal appear to be very slightly alkaline, 

 since the contents tended to become more bluish: the epithelium 

 itself does not stain, or not perceptibly. In one specimen fed as 

 above for three days, the contents of the whole gut were faintly 

 red, except the rectum which was strongly blue, with no trace 

 of purple. The chief function of the reservoir seems, on account 

 of its secretive activity, to be digestive. It may also in some way 

 aid in getting rid of the waxy matters which are so abundantly 

 excreted by these insects. It also collects a quantity of air, 

 separated from the food imbibed; there is always some air, often 

 (especially just after the moult to adult) a very large amount. 

 In the many specimens examined there was always some liquid 

 in the reservoir, and sometimes it was nearly full; the contents 

 were well shown by feeding the insects on Sonchus plants growing 

 in water deeply tinged with fuchsin. The liquid food in the ali- 

 mentary canal always appears to contain a percentage of waxy 

 matter, as does the excrement, although the greater part of the 

 wax in the latter is due to wax-dust from the anal segment wax- 

 glands, which forms a powdery film over the globule of excrement 

 immediately on its evacuation from the anus. 



Probably some sugar, and fat in the form of oil, is imbibed with 

 the food and directly assimilated; passing outwards by osmosis 

 through the peritrophic membrane and being absorbed by the cells 

 of the posterior part of the alimentary canal. The digestive 

 matters of the enzymes could also pass inwards through the mem- 

 brane and convert starch into sugar and peptonise proteids; the 

 products of digestion could then also pass outwards through the 

 membrane, ready for absorption by the cells of the epithelium. 



