28 FOREST PROTECTION 



II. The Larva. In the larvae of the Metabola, as in the adult 

 insect, the first segment is the head, the next three make up 

 the thorax, and the remainder of the body is called the abdo- 

 men; but the three regions are not so distinct as is the case 

 with the imago. The mouth parts are almost always for 

 "biting," and have the same names as in the imago. The 

 spinnarets of certain caterpillars, situated in the mouth, are 

 the apertures of long glands, which traverse the entire body. 

 If present, the antennse are rudimentary. If legs are present, 

 there are always three pairs, situated on the ventral side of 

 the thoracic segments. Sometimes there are also legs on 

 some of the abdominal segments, but these are more prop- 

 erly called pro-legs, and are not segmented. 



III. The Nymph. In the Ametabola and the Hemimetabola, the 

 anatomy of the younger stages is similar to that of the imago. 



IV. The Pupa. The pupa is called carved or masked, according 

 to the ease with which legs, antennae, mouth parts, etc., can 

 be distinguished through the pupa case. The outer web of 

 silk spun for protection by many Lepidoptera and Hymen- 

 optera is called the cocoon. 



V. The Egg. Insect eggs vary greatly in form. They may be 

 cup-shaped or kidney-shaped, crater-formed or mucronate, 

 round, oval, or canoe-shaped. Very rarely they are stalked. 



VI. Internal Anatomy. In an insect, this consists of a, the 

 Endoskeleton; b, Musculature; c, the Digestive System; (oesopha- 

 gus, crop, proventriculus, stomach, hind-gut, salivary and 

 other glands, Malpighian tubes, etc.); d, the Nervous System, 

 (brain, subcesophageal ganglion, thoracic and abdominal gang- 

 lia, nerve cord, motor and sensory nerves); e, the Circulatory 

 System, (the heart and blood); /, the Respiratory System, 

 (stigmata and trachse or trachaeal-gills) ; and g, the Reproduc- 

 tive Organs, (ovaries, ovarian tubes, and oviduct in the female; 

 spermaries and vasa deferentia in the male). 



