SOCIETIES OF THE HYMENOPTERA. 357 



of particular offices, so that a society of Hymenoptera is composed of at least three kinds of adult 

 individuals, namely, perfect females, males (whose presence in the nest is only temporary), and 

 workers, or neuters, as they are sometimes called, the last-named having upon their hands the chief 

 part, if not the whole, of the business of the construction and defence of the nest, bringing in supplies 

 of provisions, and rearing the young. The term neuters applied to them is, however, a misnomer ; 

 an examination or their anatomy proves them to be imperfectly-developed females, generally quite 

 incapable of producing eggs, and always incapable of being fertilised. Thus these societies are 

 to be regarded as including males for a short time, and at least two kinds of females, namely, 

 true fertile females, whose chief duty is the production of eggs, and infertile females, which take 

 up the other feminine duties of attending to the domestic economy, and especially to the nursing of the 

 young. It is known, chiefly from the study of the Hive Bee, that the eggs laid by the female 

 are of only two kinds, male and female eggs, and that the development of the larvae from the latter 

 into fertile or infertile females is due to differences in the food administered to them ; in fact, when a 

 hive of Bees loses its queen, or fertile female, the surviving workers are able to replace their 

 sovereign by administering the so-called " royal food " to a female larva, which would otherwise have 

 produced a worker, the only condition necessary being that the larva selected for this honour should 

 be very young. Further, it is a well-established fact that occasionally some of the workers probably 

 owing to their larvae having accidentally received a portion of " royal food " acquire a slightly- 

 increased development of the ovaries, and produce eggs, a conclusive proof of their sex. 



These facts have been pretty generally known for a great many years, but certain questions arose 

 out of them which were by no means easy to settle, although they may be all referred to the one 

 primary question at what period is difference of sex established in the progeny of these insects ? 

 Does this difference exist already in the egg 1 or is it set up subsequently by difference of treatment 

 of the larvae, just as the worker larva may be developed into a queen 1 This difficult point was 

 settled by the observations of a German pastor, named Dzierzon, who originated a theoiy, afterwards 

 further developed by the distinguished zoologist, Von Siebold, and now generally accepted, which 

 seems to explain satisfactorily all the phenomena of reproduction as exhibited in Bees. 



It has already been stated (p. 294) that in insects the eggs are fertilised during their passage 

 through the oviduct by contact with the male fertilising element, which has been stored up in 

 a special receptacle appended to that passage. Dzierzon found that the eggs laid by very old queens, 

 in which the fertilising element was exhausted, by queens which, from having crippled wings, 

 were unable to take the customary nuptial flight, and by workers which, from their structure, were 

 incapable of being fertilised, always produced males or drones ; and hence he inferred that the 

 difference of sex was established at the moment of the deposition of the egg, those eggs destined to 

 produce females or workers being fertilised during their passage through the oviduct, while those 

 which were to furnish males were allowed to pass without fecundation. Subsequent investigations, 

 carried on by Von Siebold, Leuckart, and others, fully confirmed this opinion. Fertilised queens were 

 converted into drone-breeders by exposure to considerable cold, and by the mechanical destruction of 

 the special receptacle above mentioned ; and the examination of eggs laid by fertilised queens showed 

 the presence of the fertilising filaments in those intended to produce workers, while no such elements 

 could be detected in those laid in drone-cells. The occurrence of the same phenomena has been 

 demonstrated in the case of other social Hymenopterous insects, and may safely be assumed for all, 

 although of course their demonstration is attended with much greater difficulty in the other 

 species than in the Hive Bee. By what means the female contrives, apparently at will, to fertilise 

 the eggs, or leave them unfecundated, has not yet been ascertained, nor is it very clear hov/ she knows 

 when fertilisation is necessary or unnecessary, except that in the case of the Hive Bee, and perhaps 

 of some Wasps, the different sizes of the cells prepared for rearing males and workers may furnish 

 indications. 



Very few of the Hymenoptera seem to possess special arrangements for producing sounds by the 

 friction of one part against another, but many of them, especially Bees and Wasps, produce a humming 

 or buzzing noise, principally during flight. The sound emitted appears to be due to two causes 

 first, the rapid vibration of the wings in the air, which of course can only be perceived during flight ; 

 and, secondly, according to Landois, to the vibration of certain chitinous plates, placed in the orifices 



