1. Disjunct (Disjunctum). When head, trunk, and abdomen are separated by a deep incisure.—Ex. Hymenoptera, Diptera. Plate [IV]. Fig. 2, 3, 5.
2. Compact (Compactum). When head, trunk, and abdomen are not separated by a deep incisure, but inosculate in each other.—Ex. Buprestis, Elater, and many other Coleoptera, Orthoptera, and Hemiptera.
3. Bisect (Bisectum). When the head and trunk are not separated by a suture, so that the insect consists only of two pieces.—Ex. Araneidea. Plate [V]. Fig. 4.
4. Coalite (Coalitum). When neither head, trunk, nor abdomen are separated by any incisure or suture.—Ex. Many Acari L., Phalangium, &c.
5. Multisect (Multisectum). When an insect appears to have no distinct trunk and abdomen, but is divided into numerous segments.—Ex. Scolopendra; Iulus, &c. Plate [V]. Fig. 6.
6. Cymbiform (Cymbiforme). When the margin of the thorax and elytra are recurved so as to give a body the resemblance of the inside of a boat.—Ex. Heleus, Cossyphus.
II. HEAD (caput).
i. DIRECTION.
1. Prominent (Prominens). When the head is in the horizontal line, and forms no angle with the trunk.—Ex. Carabus. Plate [I]. Fig. 1.
2. Porrected (Porrectum). When the head is prominent and elongate.—Ex. Cychrus.
3. Nutant (Nutans). When the head forms downwards an obtuse angle with the horizontal line, or trunk.—Ex. Harpalus.
4. Cernuous (Cernuum). When the head forms downwards a right angle with the trunk.—Ex. Most Gryllina and Locustina.
5. Inflexed (Inflexum). When the head forms inwards an acute angle with the trunk.—Ex. Blatta. Plate [II]. Fig. 3.
6. Turreted (Turritum). When the head is producted into a kind of columnar recurved turret or rostrum, in the sides of which, towards the end, the eyes are fixed.—Ex. Truxalis.
ii. INSERTION.
1. Retracted (Retractum). When the head is wholly withdrawn within the trunk.—Ex. Parnus.
2. Intruded (Intrusum). When the head is nearly withdrawn within the trunk.—Ex. Melasis.
3. Inserted (Insertum). When the head is partly withdrawn within the trunk.—Ex. Buprestis.
4. Exserted (Exsertum). When the head is quite disengaged from the trunk.—Ex. Tenebrio, Blaps.
5. Amplected (Amplexum). When the head is received into a sinus of the thorax.—Ex. Hister.
6. Recondite (Reconditum). When the head is wholly covered and sheltered by the shield of the thorax.—Ex. Cassida, Lampyris.
7. Semirecondite (Semireconditum). When the head is half covered by the shield of the thorax.—Ex. Silpha, Cyphon.
8. Retractile (Retractile). When an insect can at pleasure exsert its head, or withdraw it within the trunk.—Ex. Hister, Larva of Lampyris.
9. Versatile (Versatile). When the head can turn nearly round.—Ex. Hymenoptera, Diptera.
10. Pedunculate (Pedunculatum). When the head is constricted behind into a distinct neck.—Ex. Apoderus Coryli, &c.
11. Sessile (Sessile). When the head does not move in the socket of the trunk, but is attached to it by a kind of ligament.—Ex. Hymenoptera, Diptera.
iii. TERMINATION.
1. Clypeate (Clypeatum). When the Nasus, Genæ, &c. are dilated so as to shelter and overshadow the mouth.—Ex. Scarabæus, Copris, &c. Plate [XIII]. Fig. 14.
2. Capistrate (Capistratum). When the anterior part of the head is attenuated and subelongated into a kind of flat rostrum or muzzle.—Ex. Nitidula. Plate [XIII]. Fig. 13.
3. Rostrate (Rostratum). When the anterior part of the head is elongated and attenuated into a cylindrical or many-sided rostrum or beak.—Ex. The weevils (Rhyncophora). Plate [XIII]. Fig. 12.
4. Buccate (Buccatum). When the Nasus and anterior part of the head are inflated.—Ex. Conops and other Diptera. Plate [XIII]. Fig. 16.