13 
i:\TltODUCTIOX. 
rangement; the reproductive glands are symmetrical 
and double, the efferent ducts join a common duct 
before opening. The female sexual organs consist 
generally of the ovaries, oviduct, uterus, and vagina; but 
there is often a large number of accessory appendages, 
sometimes present, sometimes absent. Indeed it is seldom 
that all parts are present together, one or several being 
wanting. In neuter bees (barren or undeveloped females), 
the ovaries are deficient, though the evacuating ducts are 
constant. The females are usually larger than the 
males; this is strikingly the case where the females are 
wingless, the males winged; the antennse and the tarsi 
often differ considerably in the sexes. Insects are 
generally oviparous, though some are ovo-viviparous. 
Various forms of agamogenesis, that is to say, pro¬ 
duction without the union of the sexes, have been 
observed amongst insects. Females with a reproductive 
apparatus provided with a receptaculum seminis may 
produce either embryos, as Lecanium hesperidum and 
Chernies abietis amongst the Coccina, or ova as Psyche 
helix , Solenobia liclienella , and S. triquetrella amongst 
the Lepidoptera ; or they may produce wingless queen 
bees and winged queens as amongst Hymenoptera. 
In this class of cases sexual may alternate with asexual 
production, and it is most curious to observe that all 
male bees are produced from unfertilized eggs, while 
only the fertilized bee-egg will develop into a female or 
a perfect queen. Again, females with reproductive ap¬ 
paratus more or less imperfect, may produce either eggs, 
as happens with the “workers” or neuters amongst bees, 
whose produce is probably always males, or they may 
produce embryos as is the case with the Aphides, in 
