101 



You will notice there are two colors of bugs — red and black. Is 

 there any way to get rid of them'? Poison won't do it, for I have 

 tried London purple. They suck the sap mostly, although I think 

 later in the season they eat the leaves some, but am not sure of it. 

 They work on pear worse than others." 



The first of these species, Dolerus arvensls, was originally de- 

 scribed by Thomas Say in 1824, and the second, less common but still 

 abundant, by Beauvois, in 1805. Although the larvae of the former, 

 at least, have been known for a long time to feed upon the leaves 

 of willow, they have not otherwise, so far as I am aware, been 

 suspected of any injury to vegetation of economic importance, all 

 the references to them in the literature of entomology being of a 

 strictly technical character. From other insects occurring in similar 

 situations, with which they are at all likely to be confounded, they 

 may be distinguished by the following characters in addition to 

 those of the family Tenthredinidae, to which these insects belong : 



The first, Dolerus arvensis, is a little more than one-third of an 

 inch in length by about one-third as wide, and measures not far 

 from two-thirds of an inch across the extended wings. The head 

 and body are dark steel blue except the thorax, which is variegated 

 with yellow and black. 



The other species, Dolerus hicolor, is a trifle smaller than the 

 first, brownish yellow except the wings, the head, the middle of the 

 thorax, and the legs, all of which are black. 



Both these insects are abundant everywhere in early spring, and 

 the larvffi of both, similar in appearance to green caterpillars, but 

 distinguished by the possession of eleven pairs of legs, feed upon the 

 leaves of the willow a little later in the season. 



Careful watching in the field soon convinced me that these saw- 

 flies were neither biting nor piercing the buds or flowers, but that 

 they were merely licking off the semi-fluid exudation from the sur- 

 face of the bud scales. Dissecting the specimens and examining the 

 contents of their stomachs with the microscope, I found only a clear 

 fluid, without a trace of solid matter except occasional spheres con- 

 sisting of clusters of threads of fungous parasites. Critically search- 

 ing the surface of a bud scale which these flies had but just 

 worked over, I saw that no injury whatever had been done to the 

 tissues of the plant, even the slender hairs with which the scales 

 were covered being wholly undisturbed. Watching the flies with a 

 glass, I could see that their biting jaws remained ail the time closed, 

 but that their flap-like maxillae were continually employed in mop- 

 ping up the moisture from the viscid surface, and as they have no 

 mouth parts capable of piercing the substance of a plant, it was 

 clear that no injury was being done. Finally, I confined a lot of 

 the saw flies in a breeding cage with pear buds not yet open. The 

 insects industriously w^orked over the surfaces of the unopened buds 

 and even entered the flowers as they expanded, but did neither any 

 visible injury whatever. The buds afterwards all opened out in 

 abundant bloom, and remained fresh for several days, while the 

 poor saw flies, having lapped- up all the syrup avaflable, starved to 

 death in the midst of the uninjured blossoms. A little experiment 



