154 



sparrows do more liarm than good. The style of the book is attractive, 

 but the statements, many of them, will not bear the test of scientific in- 

 quiry. 



OCCASIONAL DEVELOPMENT OF WINGS IN NORMALLY APTEROUS 



HEMIPTERA. 



Mr. J. W. Douglas, in a review of Mr. F. B. Pascoe's recent work on 

 the Darwinian theory of the origin of species ( The EntomolofiiHts' Monthly 

 Magazine, Ajjril, 1891, j). 109), calls attention to the statement that " Some 

 of our Hemiptera, Nabis, Pithattus, Pyrrhocoris, etc., ordinarily wingless, 

 are sometimes found in hot summers to have well-develo])ed wings." 

 As Mr. Douglas remarks, all these species normally have rudiments of 

 elytra, but there are other species quite apterous in which at times 

 macropterous individuals appear, in which case the respective forms are 

 so divergent as to be considered distinct. But he does not believe that 

 such dimorphism occurs only in hot summers, and mentions having ob- 

 served it in cold seasons also, when there was nothing exceptional in 

 the weather to favor such development. He believes that at present 

 no satisfactory explanation can be given. May it not be that the devel- 

 opment of wings is dependent somewhat on the food supply of the insects, 

 and they are produced to enable a more extended migration, rendered 

 necessary by a diminution of the food supply or the overdevelopment 

 of the species? The abnormal appearance, locally, of winged specimens 

 of a wingless species can not be satisfactorily explained by the theory 

 of a reversion to a winged ancestral tyi)e, since this would account for 

 isolated cases, but would hardly explain the general appearance of 

 winged individuals. 



AN ARGUMENT AGAINST SPRAYING FOR SCALE-INSECTS. 



In the California Fruit Grower of January 31 we notice a com. 

 munication from Mr. F. Eighter, who states that at the last meeting of 

 the Campbell Horticultural Society the subject of the best materials to 

 destroy the brown apricot scale was discussed, and that it was generally 

 concluded that it was better not to spray at all, as those orchards which 

 had not been sprayed were found upon examination to be freer from 

 scale than those which had been sprayed annually. Orchards which 

 had not been si)rayed and which were at one time badly infested with 

 this scale were said to be now entirely free from the pest. If these facts 

 are correct the deduction is also correct, but it is evident that some 

 important natural enemy of this bark louse has been at work. It was 

 the supi)osition of the members of the society that the Vedalia had 

 killed off the scale, but this is entirely contrary to the experience of our 

 agents and correspondents. It seems certain that Vedalia will prey 

 upon nothing in this country but Icerya purchasi. The item in its 

 ])resent shape, however, is calculated to do considerable harm, and no 

 horticulturist should neglect spraying in consequence of this exceptional 

 experience. 



