1:^1 



A spL'cics of yclKnv -jacket {]'ts/>(i) visits the hawthorn for the 

 purpose of sccurinf^ phiiit lice for its huvae. Various species of 

 flics (Diptcra) were found to visit the phmt-lice to take from 

 them the sweet honeydew and these winded aerial marauders 

 take care to keep out of reach of the ants, which they are read- 

 ily enabled to do. Another and larger species of ant was occa- 

 sionally found on the hawthorn. While it was quite evident that 

 it was also in quest of the honeydew of the /Iphis, it was equally 

 evident that it was mortally afraid of the smaller but decidedly 

 more pu^Miacious honey-ant, making ever)' effort to keep out of 

 the way. 

 • Another la(l\'bird iyCoxincUa caHfoniica) also feeds upon the 

 Aphis, but is nuich less voracious in its appetite than the I lippo- 

 daiiiia. The ladybirds were however not sufficiently numerous 

 to destroy all of the aphides which multiply so rapidly that there 

 seemed to be no diminution in their number, in spite of these 

 numerous life-destroying enemies. Later in the season (the 

 latter part of July and the early part of August), the Aphis 

 began to disappear gradually so that practically none remained 

 b)' the middle of September. This sporadic and often sudden 

 disappearance of ApJds has been noted frequently but is not as 

 yet satisfactorily explained. The natural enemies as ladybirds 

 and the fungus referred to are evidently not the only factors con- 

 cerned in these disappearances. Various birds, as sparrows and 

 others, are often seen to feed upon the Aphis, scooping them up 

 in large numbers by a peculiar side twist of the bill. 



A black fungus lives upon the leaves, leaf-stalks and }'ounger 

 branches of the hawthorns, causing them to become unsightly in 

 ap[)earance, although no serious damage is done. It is very 

 evident that the plant-lice are the cause of this fungous invest- 

 ment as the growth staits in \.\\c .Iphis and then spreads over the 

 plant. Besides this fungus, there are other vegetable symbionts, 

 as various algae, bacteria and other fungi, which, however, have 

 no apparent influence upon the life history of the host plant 

 (hawthorn). The various more serious diseases of the hawthorn, 

 due to fungi and insects, are not touched upon in this paper as 

 this would further complicate the biological relationship and 



