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XV. On the manner in ichich the ravages of the larvae, 

 of a Nematiis, on Salix cinerea, are checked by 

 Picroraerus bidens, L. By Albert Muller, 

 F.L.S. 



[Read 2nd December, 1872.] 



On the 30tli September last I happened to saunter over 

 the summit of Shirley Heath, when my attention was 

 attracted by an isolated bush of Salix cinerea grooving in 

 a slight hollow of the heath. Ah-eady from a distance I 

 could perceive that something unusual had taken place, as 

 all the top shoots were entirely deprived of their foliage. 

 A closer examination revealed the following state of things. 

 Hundreds of saw-fly larvte in different stages of growth 

 were feeding on the middle and lower branches. The top 

 branches had entirely been cleared by them of every leaf, 

 the bare branches retaining only the mid-ribs and a few 

 shreds of the stronger lateral ribs. Each leaf, or more 

 correctly the series of leaves of each tmg, were occupied 

 by individuals of the same size ; thus separate twigs ex- 

 hibited distinct broods, of which (to judge by size only) 



1 counted four of different ages. 



While feeding, the individuals of all these broods clung 

 to the edges of the leaves by means of their three pairs of 

 pectoral feet, the body resting curled up mostly on the 

 under side of the leaves, but directly a twig was shaken 

 the hind-bodies were violently thrown upwards, and then 

 generally remained in that position for some time, until the 

 branch was again disturbed, when a whipping to and fr'o of 

 most of the upturned hind-bodies would follow. I could 

 not perceive the emission of any odour or secretion so long 

 as the larvfB were not actually handled, but if taken up by 

 the fingers a foetid smell became at once perceptible. The 

 following description is taken fi'om a frill-fed larva, cap- 

 tured on the ground below the bush : — 



Length, 2 centimetres; width, 2\ millimetres; width 

 of tlie head, 2 millimetres; 20 feet (6 pectoral, 12 ventral, 



2 anal) ; between the 3rd pectoral pair and the 1st true 

 ventral pair, a slight conical protuberance on each side 

 seems to represent an abortive pair of ventral legs ; the 

 11th ventral segment is footless. Head shining black; 



TRANS. ENT. SOC. 1872. — PART IV. (dEC.) X 



