HONEY-DEW. 



272 



HONEY-DEW. 



There are certain plants whicb , under cer- 

 tain conditions, it is said, exude a sort of sac- 

 charine substance from the leaves, but, strict- 

 ly speaking, this is not honey-dew. The 

 ordinary " stuff " that is gathered by the 

 bees, commonly called honey-dew, is nothing 

 but a. secretion from plant-lice. There are 

 several species of honey-dew lice, among 

 whicli may be named Lecanium tilice, that 

 attack the basswoods; Lecnnium tulipifera, 

 of the tulip-tree, often called " poplar,'' and 

 the scale or bark louse that attacks maple- 

 trees, Fulvinaria innumerabilis (Rath. ). Prof. 

 Cook, formerly ot the Michigan Agricultural 

 College, now of Claremont, Cal., professor 

 of entomology, and a bee-keeper of long ex- 

 perience, thus describes these lice : 



The maple-tree scale or bark louse {Pidvinaria in- 

 numerabilis Rath.) consists at this season (1884) of a 

 ■brown scale about five-eighths of an inch long, which 

 is oblong, and slightly notched behind. On the back 

 of the scale are transverse depres-sions, marking seg- 

 ments. The blunt posterior of the insect is raised by 

 a large dense mass of fibrous cotton-like material, in 

 which will be found about 800 small white eggs. These 

 eggs falling on to a dark surface look to the unaided 

 eye like flour; but with a lens they are found to be ob- 



£ LOUSE 



long, and would be pronounced by all as eggs, at once. 

 This cotton-like egg-receptacle is often so thick as to 

 raise the brown scale nearly a fourth of an inch. 

 The scales are found on the under side of the limbs 

 of some trees, and are often so thick as to overlap each 

 other. Frequently there are hundreds on a single main 

 branch of a tree. I find them on basswood, soft and 

 hard maple, and grapevines, though very much more 

 abundant on the maples. 



Another feature, at this mature stage of the insect, is 

 the secretion of a large amount of honey-dew. This falls 

 on the leaves below, so as fairly to gum them over, as 

 though they were varnished. This honey-dew is much 

 prized by the bees, which swarm upon the leaves. If 

 such honey-dew is plea.sant to the taste, as some aver, I 

 should have no fear of the bees collecting it. 



From the middle to the last of June, the eggs begin 

 to hatch, though hatching is not completed for some 

 weeks after it begins, .so we may expect young lice to 

 hatch out from late in June till August. 



The young lice are yellow, half as broad as long, 

 tapering slightly toward the posterior. The seven 

 abdominal segments appear very distinctly. The legs 

 and antenuje are seen from the other side. As in the 

 young of all such bark-lice, the beak, or sucking-tube, 

 is long and thread-like, and is bent under the body till 

 the young louse is ready to .settle down to earnest 

 work as a sapper. Two hair-like appendages, or .setse, 

 which soon disappear, terminate the body. 



The same writer, in the American Bee Jour- 

 nal for January, 1899, gives his reasons for 

 doubting the plant origin of honey-dew. He 



says : 



1. I now have carefully examined this secretion for 

 years, whenever seen, and have always found either 

 aphides — plant-lice; coccids — scale insects; other 

 hemipterous bugs ; or else larvse of in.sects (these are 

 reported to me) often working in scores — to be the 

 source of this nectar. This gives strong presumption 

 that such is always the source of honey-dew. 



2. We have reason to believe, in the economy of 

 Nature, that energy is never expended by plant or 

 animal that does not in some way benefit by such out- 

 go. We are easily able to see how the insects profit 

 by the secretion of this nectar. They thus lure bees, 

 ants, wasps, etc., to their immediate presence, and 

 these in turn repel the birds which else wovild feed on 

 and destroy the insects. 



I once noticed an exhibit of this function in Michi- 

 igan, so palpably displayed that to doubt it was im- 

 possible. The lecanium tilicE — a large bark louse- 

 was thick on a linden-tree close beside my study win- 

 dow. In early spring the beautiful song sparrow 

 commenced to feed on the young scale insects which 

 thickly dotted the leaves. Suddenly the bees and 

 other sweet-loving in.sects commenced to visit the 

 same leaves for the honey-dew which dropped from the 

 coccids, and the birds at once cea-sed to come. In a few 

 days cold, or, preferably, nectar in other places, kept 

 the bees and their companions from the place, and 

 the birds again commenced their good work. This 

 alternation of bird and bee visits occurred several 

 times. Such observations make the value of the ex- 

 pensive secretion to the insects clearly evident. 



On the other hand, the honey-dew always becomes 

 foul with the black smut or fungus that attacks sweet 

 substances on tree or bush. We can hardly doubt 

 that it is a serious evil to the plants, and are unable to 

 see any good that comes to the plant from it. I fully 

 believe it is always harmful to vegetation, and I feel 

 certain that plants do not originate it to their own 

 hurt. 



I referred above to certain acorn-infesting larvse 

 that secrete nectar. I have never seen them, but 

 have often heard of such — principally from Missouri — 

 so often that I think they may be more than a myth. 

 Yet I am free to say that I should feel more certain if 

 I actually saw them. I can see how oak-tree plant- 

 lice, which are by no means rare, might lead to an 

 erroneous conclusion. 



Ergot — a fungus which attacks rye and other plants 

 — is also said to secrete honey-dew. If this be true, 

 then I feel sure that the sweet in some way benefits 

 the fungus. If it does the fungus no good, then I be' 

 lieve it, too, has other origin. 



In California, where scale insects and aphids are .so 

 common, it is very easy to study the honey-dew, and 

 the black repulsive fungus, which our orchardists de- 

 nominate " smut." The walnut-tree, this season, has 

 been infested generally with an aphid, and honey-dew 

 I and smut have always attended it. 



