180 Psyche [December 



It would seem possible that the diastase of the plant may be 

 imbibed with the rest of the juices, and assist the action of the 

 digestive secretions of the insect. It does not seem probable 

 that the reservoir is a mere store-vessel only, to be drawn upon 

 intermittently. It may perhaps be so spacious in order to give 

 increased area for the digestion and absorption of a comparatively 

 innutritious food, l so that it may be rapidly passed on and fresh 

 supplies taken in. On the other hand many Homoptera feeding 

 in like manner on the same plants have no reservoir, though per- 

 haps in these the area of the gut is increased in other directions. 



In the nymph just hatched the reservoir does not always enter 

 the head, but soon afterwards it does so, and is completely formed 

 at the time the nymph hatches out. In the head the reservoir 

 lies practically free, but is slightly attached by connective tissue 

 to the front of the head-capsule. 



In the nymphs, at each successive moult, there is an almost 

 total and sudden degeneration and disappearance of the epithe- 

 lium of the alimentary canal, very little remaining but the muscu- 

 lature and peritoneal membrane. The epithelium is then very 

 quickly regenerated. 



The muscles of the oesophagus consist of two layers of stout 

 annular fibres crossing each other almost at a right angle (fig. 4). 

 The nuclei of the oesophageal valve are larger than those of the 

 rest of the oesophagus, and rounder than those of the mesenteric 

 epithelium. They probably secrete more actively than the rest 

 of the oesophageal cells, since the six chitinous folds of the intima 

 are much thicker at the valve, forming six cushions or pads at 

 its summit. There seem to be no special glandular cells in the 

 oesophagus, but the salivary-glands and reservoirs in this insect 

 are very voluminous. They give a decidedly alkaline reaction 

 when tested with litmus. Their secretion would probably convert 



1 That it is a somewhat innutritious food compared with that of carnivorous insects may 

 be inferred from the time the insect spends in feeding, and the large amount of excrement 

 continually voided, compared with a carnivorous insect. And besides the faeces must be in- 

 cluded as excrement the large quantity of waxy substances excreted from various parts of the 

 body. For although the wax of Homoptera may have become useful in certain ways, such as 

 a covering for their eggs when laid, etc., yet originally it can have had no such use, but was a 

 waste product to be gotten rid of. Yet the phloem of plants contains in the sieve-tubes much 

 proteid matter in the form of a nitrogenous slime, which must be sucked up by the insect along 

 with the rest of its liquid food. Perhaps the Homoptera require such large quantities of food 

 because it is not in a very concentrated form. 



