700 EXTERNAL ANATOMY OF ENSECTS. 
4 
large a little upon it. You would be surprised, and not 
without reason incredulous, were I seriously to assert 
that these insects lift their weighty posteriors by means 
of a rope and pulley ; yet something like this really does 
take place, though not with all in a manner equally 
striking. The point of articulation in the insects in ques- 
tion, except in Evania, is at the base of the metathorax 
just above the posterior pair of legs: here you see a small 
orifice, either insulated or connected by a narrow open- 
ing with the larger one, when the abdomen is removed, 
which in many instances, as in the common wasp, is sur- 
mounted by another still smaller, through which, if you 
examine it attentively, you will find there is transmitted 
a flat and sometimes broadish ligament or rather tendon, 
in which the levator muscles of the abdomen, attached 
by their other end to the metaphragm, terminate: an- 
other minute orifice above the base of the pedicle affords 
a point of attachment to the tendon, so as to give it prize 
upon the abdomen. Here the upper orifice in the trunk 
is the pulley (trochlea)*, the tendon is the rope (funicu- 
lus *, and the abdomen is the weight to be lifted. When 
the muscles contract, the tendon running over the edge 
of the aperture, is pulled in, and the part just named is 
elevated; and when they are relaxed the tendon is let 
out, and it falls. Some little variation in the structure 
takes place in different tribes: thus, in the Formicidae, 
Scoliade, &c., instead of a separate orifice, the part I 
call the pulley is merely an upper sinus of the large ori- 
fice that receives the pedicle of the abdomen. The shape 
of these orifices, both of the trunk and abdomen, varies 
4 Prats IX. Fic. 13. F” is the tendon, G’ the aperture in the 
abdomen C, and a, the aperture in the trunk B. 
