MOTIONS OF INSECTS. 309 
a vertical direction. So that, as long as it keeps moving, 
little bunches of the legs are alternately in and out from 
one end to the other of its long body; and an amusing 
sight it is to see the undulating line of motion succes- 
sively beginning at the head and passing off at the tail. 
—The motion of centipedes (Scolopendra), as well as 
that of this insect and its congeners, is retrogressive as 
well as progressive. Put your finger to the common 
one (S. morsitans, L.), and it will immediately retro- 
grade, and with the same facility as if it was going for- 
wards. This difference, however, is then observable— 
it uses its four hind legs, which, when it moves in the 
usual way, are dragged after it. Almost all the other 
apterous insects, as well as many of those in the other 
orders, can move in all directions; backwards, and to- 
wards both sides, as well as forwards. Bonnet mentions 
a spider (not a spinner) that always walked backwards 
when it attacked a large insect of its own tribe; but 
when it had succeeded in driving it from a captive fly, 
which however it did not eat, it walked forwards in the 
ordinary way?. _ 
Insects vary much in their walking paces: some 
crawling along; others walking slowly; and_ others 
moving with a very quick step. The field cricket 
(Acheta campestris, F.) creeps very slowly—the bloody- 
nose beetle (Chrysomela tenebricosa) and the oil-beetle 
(Meloe Proscarabeus) march very leisurely; the spider- 
wasps (Pompilus, F.) walk by starts, as it were, vibra- 
ting their wings, at the same time, without expanding 
them; while flies, ichneumons, wasps, &c., and many 
2 (Euvr. uu. 426. 
