INSECTA. 391 



or because being fixed very loosely, they are lost on the first flight ; 

 as has been observed in Sphinx 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 maxilla), 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 maxillae 

 are placed two very short palps, consisting of one or two, at most of 

 three, joints. The under-lip (labium) 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 antennae 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 larvae are called caterpillars 

 (erucce, chenilles, JKaupen, 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 joints ; 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 ; 



