INSECTA. 391 
or because being fixed very loosely, they are lost on the first flight, 
as has been observed in Sphinw fuciformis. 
Amongst the oral organs (compare above, p. 249) is seen a small 
upper-lip, often scarcely visible, which is of a triangular or conical 
form ; the mandibles are small, immoveable, and remote from each 
other. These parts exist in a rudimentary state alone. The prin- 
cipal part of the organa cibaria is the spiral tongue, formed of two 
long threads (the mawillw), which are excavated on the inside, else- 
where even, and run out to a fine extremity; when these two 
plates are laid towards each other, the two half canals form a com- 
plete canal in the axis of the tongue. At the base of the maxille 
are placed two very short palps, consisting of one or two, at most of 
three, joints. The under-lip (/abiwm) is triangular and flat, and 
bears two large palps, which consist of three joints ; these palps are 
covered with hairs, and mount with their points turned upwards on 
both sides of the tongue, which rolled up in a spiral lies hidden 
between them, whenever it is not in use. In some nocturnal lepi- 
doptera the tongue is very short and not adapted for sucking. 
The antenne of these insects differ in form, but always consist of 
numerous joints. The two compound eyes are large; in many 
species there are in addition two simple eyes present. The three 
rings of the thorax are always connected immoveably with each 
other; the middle piece (mesothorax) is the largest. The wings 
are large and not folded; in the females of some species they are 
reduced to small rudiments, or are entirely wanting. There are five 
joints in the tarsus of all the feet. The abdomen consists of six or 
seven rings, without sting or borer, as in the preceding order. 
The metamorphosis is complete. The larvee are called caterpillars 
(eruce, chenilles, Rawpen, rupsen). The body of caterpillars con- 
sists of twelve rings exclusive of the head. There are on each side 
nine air-slits; for the second, third and last ring are without them. 
The normal number of feet in caterpillars is eight pairs; the fourth, - 
fifth, tenth and eleventh ring have no feet. On the first three rings 
three horny feet are placed, which have a conical form, and consist 
of joints; the last joint has the form of a bent nail. These 
six feet answer to those of the perfect insect. The remaining ten 
feet (some species have only eight, six, or four) are membranous 
and without joimts ; they disappear in the perfect insect. On the 
underside they have a flat surface, which the insect is able to expand 
and contract, and which is surrounded by a coronet of numerous 
small hooks. The head is horny, and has six simple eyes on each side ; 
