66 STATES OF INSECTS. (Egg.) 
as—their exclusion—situation—substance—number—size 
—jfigure—colour—and period of hatching. 
i. Exclusion. The exclusion or extrusion of the im- 
pregnated eggs takes place, when, passing from the ovary- 
into the oviduct, they are conducted by means of the 
ovipositor, in which it terminates, to their proper situa~ 
tion. By far the.greater number of insects extrude them 
singly, a longer interval elapsing between the passage of 
each egg in some than in others. In those tribes which 
place their eggs in groups, such as most butterflies and 
moths, and many beetles, they pass from the ovaries 
usually with great rapidity; while in the Ichneumonidae, 
Sphecina, Gistri, and other parasitic genera, which usu- 
ally deposit their eggs singly, an interval of some mi- 
nutes, hours, or perhaps even days, intervenes between 
the extrusion of each egg. One remarkable instance of 
the former mode I noticed in my letter on the Perfect 
Societies of Insects? ; another may be cited, to which you 
may yourself be a witness—lI allude to that common 
moth, vulgarly called the Ghost (Hepiolus Humuli), which 
lays a large number of minute black eggs, resembling 
grains of gunpowder, and ejects them so fast that, ac- 
cording to De Geer, they may be said to rum from the 
oviduct, and are sometimes expelled with the force of a 
popgun’, <A Tetrapterous insect, the genus of which is 
uncertain, is said, when it is taken, to discharge its eggs 
like shot from a gun*. And a friend of mine, who had 
observed with attention the proceedings of a common 
* See Vot. II. p. 36. > De Geer i. 494—. 
© Called by M. PAbbé Preaux, who observed it near Lisieux in 
Normandy, Mouche Baliste. N. Dict. d’ Hist. Nat. xxi. 442. 
