NATURAL HISTORY SOCIETY OF GLASGOW. 225 



of caterpillars, and on the development of the insects. Referring 

 to the brown marks on the larvae of Smerinthus, he showed that 

 they simulated the leaf fungi and the mite galls so common on 

 food plants, and thus had an additional means of concealment 

 besides the green colour, in imitation of that of the leaves. He 

 then discussed the striking change in coloration which many larvae 

 of Tenthredinidae underwent at the last moult and immediately 

 before pupation. This change he showed, by referring to Cladius 

 viminalis, Nematis viminalis, &c, was of a protecting nature, 

 either in rendering the larva less or more conspicuous, according to 

 the habits of the creature. N viminalis, for example, living in 

 galls, has no need for coloration; but before pupation, and when it 

 leaves the galls, it becomes slate coloured, which assimilates it 

 with the sand on the river-bank on which it lives, and up which 

 it crawls to a place where it will not be so much exposed to in- 

 undation. Cladius viminalis, on the other hand, assumes a more 

 gaudy coloration at the last moult, so that it may be more readily 

 seen — the reason of this being that the larvae live several on a 

 leaf, and thus they are conspicuous enough; but when they reach 

 maturity they separate, in order to reach a safe resting-place — 

 generally up trees. Thus a more gaudy coloration is of advantage 

 to them during this transition period, as the orange colour renders 

 them visible at a distance of several yards, and when seen they are 

 avoided by insectivorous animals. • 



The second part of the paper was taken up with the subject of 

 Parthenogenesis in the Tenthredinidae. Mr. Cameron stated that 

 this phenomenon exists under two phases — first, with species which 

 have males and females, tolerably common, the parthenogetic brood 

 in this case being always male; and second, with species having no 

 known males — the result in this case being females. Details were 

 given of the experiments of the author with various species, as 

 well as of observations communicated to him by Mr. J. E. Fletcher 

 on Nematis jxdliatus and N. gallicola, all proving the very general 

 occurrence of Parthenogenesis in this family. In conclusion, the 

 author stated that, from observations he had made on one or two 

 maleless species, he was inclined to believe that the number of 

 perfect insects which reached maturity bore a small proportion to 

 the number of larvae — in other words, the larvae have less vitality 

 than those of bi-sexual insects, and thus the species was enabled to 

 flourish only by the great number of eggs it laid. Still the difn- 



