574 JAMES E. BLOMFIELD. 



The insect wliich produces this disease is an aphis of a 

 pnrplisli-red colour. Crushed between the fingers it leaves 

 a blood-red stain, whence it derives its German name of 

 Blood-louse, but its chief characteristic which makes its pres- 

 ence easily noted is a fluffy covering of a white or greyish 

 colour, sticky and resinous in consistence which exudes from 

 tubercles on the back of the insect, and which, from the fact 

 that it is insoluble in water, serves to protect the insect from 

 wet and damp, and to make difficult its eradication from an 

 orchard when once it is seriously invaded by the aphis. The 

 material is soluble in alcohol, and I imagine, though I can 

 speak from no practical experience, that the reason that in- 

 secticides are so useless is owing to the fact that this resinous 

 material is not removed before they are applied. 



The general structure of the Schizoneura is the same as that 

 of other aphides except that the cornicles are atrophied. The 

 rostrum in the immature forms is as long as, or longer than, 

 the body. The rostrum or haustellum is as in other Hemi- 

 ptera an extension of the labium. It consists of three joints 

 which are grooved on their upper surface to receive the setjB 

 or lancing organs which prick the juicy parts of plants to 

 cause a flow of sap on which the insects feed. The setee are 

 three in number, and represent the mandibles and maxillfB of 

 other insects. During the act of sucking the rostrum is 

 closely applied to the plant surface and secured there by 

 coarse hairs at its tip, the seta) are run along their groove 

 into the soft plant tissue, which they lance and stab to ensure 

 a flow of sap which can be sucked up partly by capillary 

 attraction and partly by a pumping action on the part of the 

 insect. 



The question whether salivary glands are present in all 

 aphides appears to be yet unsolved. They were found by 

 Buckston {' Brit. Aphides,' Ray Society) in some specimens, 

 the name of which he does not give, but in connection with 

 the present subject the matter would seem to have some im- 

 portance because it is to the secretion of some such gland 

 that we must look as a cause for the peculiar action of the 



