278 (NovetnlDcr, 



the tubular rostral setas at the same time that these are inserted into 

 the stomata or between the cells of the plant, reacts upon the vegeta- 

 ble cells and tissues. Again, with the exception of these setse, a 

 Coccid as a rule possesses no organs for piercing and cutting. I say 

 " as a rule," because it would appear from Dr. Signoret's Essai that in 

 the genus PorphyropTiora the anterior feet are " fossorial," and might 

 therefore possibly be used as cutting instruments. But in all other 

 cases, as far as I know, the feet are strictly ambulatory, and in many 

 cases they are absent altogether. Failing a mechanical instrument for 

 excavation, and also a chemical fluid for reacting on the plant-cells, 

 how do Coccids manage to form cavities, more or less deep, for their 

 habitations ? 



I do not think that the number of " burrowing " species in the 

 Family is large. Here, for the purpose of illustration, I need only 

 refer to a few typical cases, from which it will be seen how various 

 are the effects produced. An example of simple depression in a leaf 

 may be found in the New Zealand species, Otenocliiton viridis, mihi. 

 This is a Lecanid insect, very large and proportionately thick, and its 

 ventral surface is considerably (in most cases) convex. Looked at in 

 situ, it seems to be simply lying on the under-surface of the leaf, but 

 when it is removed, there is seen to be in its place a depression, not 

 very deep, corresponding to the convexity of the insect. This de- 

 pression is usually powdered with white cottony meal, more or less 

 thin, but I cannot say that there is any distinct appearance of altera- 

 tion in the tissues of the leaf. Another New Zealand insect, Bhizo- 

 coccus fossor, mihi, goes a little further. It burrows into the leaf on 

 which it lives a cavity corresponding to the size of its body, and of 

 such depth that it at last sinks into it as in a pit, and often the surface 

 of the leaf curls over the insect and partially encloses it ; a curious 

 feature of this proceeding is that the other surface of the leaf is 

 pressed up in a small conical elevation. A point which would, in this 

 instance, seem to indicate some kind of chemical action is that the top 

 of the elevation is usually dark brown, the normal colour of the leaf 

 being dark green. 



The two insects just mentioned live on leaves, and have therefore 

 soft material to work on ; but Xylococcus filiferus, Low, an insect in 

 Austria, lives in the axils of the twigs of Tilia europcea, and digs out 

 for itself a cavity in the bark of the tree. As far as I can gather 

 from J3r. Low's description (Yerh. des zoolog.-bot. Gesell., Wien, 

 1882), the hole thus burrowed out only extends "to the wood," and 

 does not go deeper, although in bis figure he seeras to show it at least 



