8474 Insects. 



one's adherence to or dissent from the opinions of others in such 

 a matter. 



I have given all the other references, as they apply either to this 

 species — of which two races or varieties appear to exist — or else to 

 a second species, which is only to be distinguished from the present 

 by the most minute characteristics. It even appears to me to be 

 very probable that there are two species having the same habits, but 

 living on two distinct species of willow. Although I have lately 

 taken great pains to get both these species, I have not hitherto suc- 

 ceeded. If eventually, upon rearing the other species, it should be 

 ascertained that it is actually distinct, the references will probably be 

 found to apply solely to this latter, which must then take the name of 

 Nematus Gallarum, Hartig. 



In order to explain my meaning more clearly, I must remind my 

 readers that De Geer speaks of galls on Sahlweiden (Salix cinerea, L.), 

 and that Hartig mentions the same species of tree. My galls, on the 

 other hand, are from the Salix repens. Besides this, the above- 

 mentioned authors speak of gray caterpillars ; whereas mine were 

 glassy white when young, and yellow or orange when full-grown. 

 Lastly, I may add that for years, in a certain garden on the banks of 

 the Maas, and the high sea-wall of Schieland, outside Rotterdam, 

 were a number of willows which were every year covered with galls : 

 these galls were at first green, and afterwards turned to yellow, but 

 never became red ; and I remember finding them tenanted by gray 

 slate-coloured larvae. Now, these may have belonged to another spe- 

 cies, possibly De Geer's. Last year, when I visited the garden in 

 question, with the intention of investigating this matter, I found the 

 willows had been cleared away ; and other willows standing on the 

 same bank, and in the neighbourhood of, although at some distance 

 from, the former plantation, had no galls on them. I had hoped that 

 Dr. Wttewaal would have been able to meet with galls on the willows 

 bordering the Yssel, but this has not hitherto been the case. 



In the month of September galls may be found on the dunes in the 

 neighbourhood of the Hague, and near Noordwijk (especially in the 

 last-named place, behind the church-yard), growing on the hard 

 short-leafed dune-willow : these galls look like cherries (see fig. 1). 

 They are always attached to the under side of the leaf, and are very 

 shining and quite destitute of hairs, so that they are very different 

 from those mentioned by Hartig. Some are larger than others ; the 

 one represented is one of the largest : they are yellowish green, yel- 

 low or red ; the surface is studded with several minutely granular 



