Maskell. — On Coccididae. 59 



short joints, but the joints are somewhat confused ; on the last 

 is a long hair. Feet slender : tibia shorter than the tarsus ; 

 tarsus slightly dilated ; upper digitules very long knobbed 

 hairs, lower pair apparently wanting. On the dorsum are two 

 marginal, two median, and two intermediate rows of figure-of-8 

 spinnerets. 



Male unknown. 



Hab. In Australia, on Casuarina equisetifolia and C. 

 quadrivalvis : Mr. French has sent me several specimens. 



This remarkable insect, as observed above, does not seem 

 to fit into any known genus. It is not clear by what process 

 the burrowing into the bark is eifected. The larva does not 

 seem to do it, at least to any great depth, because the female 

 of the second stage is, as stated just now, found scarcely 

 buried. As for the gall-like swellings of the plant, they may 

 be accounted for in the usual way as the result of "irritation 

 caused by the suction of the insects;" yet I see nothing to 

 indicate that Frenchia has any organs of irritation not pos- 

 sessed by other Coccids. This question of gall-formation 

 merits attention. Another Brachyscelid — B. ovicola, Schrader 

 — forms great egg-shaped domiciles, which are only attached to 

 the plant by their extreme tips. I possess specimens of these 

 nearly 2in. long, on twigs scarcely Yt^in. thick : there must be 

 something more than " irritation " here. But, if there exist in 

 certain species special organs with which they so act on a 

 plant as to produce galls, it would be interesting to discover it. 

 After several years' minute investigation of many (perhaps 

 three hundred) different Coccids, no organ of the kind is known 

 to me. Yet, as I have observed elsewhere (Entom. Monthly 

 Mag., November, 1890), some Coccids produce galls, some 

 make cavities, others exercise no influence on the form of a 

 plant. As between, say, Aspidiotus nerii, Lecanium hesperiduvi, 

 Xylococcus filiferus, Bhizococcus fossor, Frenchia casuarina, 

 Brachyscelis ovicola, what is the difference of organs in each 

 which results in the different action of each on the food-plant? 

 Long ago Eeaumur and Bonnet attempted to explain plant- 

 galls on the theory that the softer portions of the structure 

 would tend to growth on the lines of least resistance, and conse- 

 quently would flow towards a punctui'e by an insect. The 

 explanation, however, fails to show why in the great majority 

 of cases neither galls, cavities, nor distortions occur, whilst a 

 minority of Coccids bring about one or other of the three. In 

 Insect Life, vol. iii., No. 7, p. 343, Professor Eiley, comment- 

 ing upon my paper in the Entomological Monihly Magazine 

 just mentioned, expresses the opinion that "a j)oisonous prin- 

 ciple must exist, however difficult to detect." Just so ; but it 

 would be interesting to have the subject worked out. Time 

 will not permit of my entering upon this investigation, and, 



