The tick is generated from couch-grass. The cockchafer comes
from a grub that is generated in the dung of the cow or the ass. The
cantharus or scarabeus rolls a piece of dung into a ball, lies
hidden within it during the winter, and gives birth therein to small
grubs, from which grubs come new canthari. Certain winged insects also
come from the grubs that are found in pulse, in the same fashion as in
the cases described.

Flies grow from grubs in the dung that farmers have gathered
up into heaps: for those who are engaged in this work assiduously
gather up the compost, and this they technically term 'working-up' the
manure. The grub is exceedingly minute to begin with; first even at
this stage-it assumes a reddish colour, and then from a quiescent
state it takes on the power of motion, as though born to it; it then
becomes a small motionless grub; it then moves again, and again
relapses into immobility; it then comes out a perfect fly, and moves
away under the influence of the sun's heat or of a puff of air. The
myops or horse-fly is engendered in timber. The orsodacna or budbane
is a transformed grub; and this grub is engendered in
cabbage-stalks. The cantharis comes from the caterpillars that are
found on fig-trees or pear-trees or fir-trees--for on all these
grubs are engendered-and also from caterpillars found on the dog-rose;
and the cantharis takes eagerly to ill-scented substances, from the
fact of its having been engendered in ill-scented woods. The conops
comes from a grub that is engendered in the slime of vinegar.