IXTRODUCTIOX. 



Fig. 3. 



it is joined by membrane ; sometimes, however, it is contracted behind 

 and lengthened, and is occasionally behind the constriction expanded 

 into a semi-globular knob or condyle, which acts as a sort of ball and 

 socket joint and admits of free movement in every direction (as in some 

 genera of the Truncatipennes, the Brenthidee, &c.); in front of the head 

 there is usually a suture stretching right across between, or in front of, 

 the antenna3 ; this is called the clypaal suture, and the part it cuts off 

 from the head is called the di/jiaus ; if, as often is the case, an apparent 

 suture is seen in front of the clypeus it is due to the junction of the 

 lahrum or upper lip which will be spoken of under the mouth organs : 

 the clypeus is sometimes called the ejnstoma ; according to some authors 

 when large it is styled the clijpeus, and when small the epistoma, but 

 this latter term is used very loosely and seems by some writers to be 

 applied to the lahrum or to the lahrum and clypeus combined, thus 

 including, as its name implies, all the parts over the mouth.- The 

 insertion of the antennas relatively to the clypeus is in some groups a 

 very important character ; thus in the Cicindelidse the clypeus extends 

 on both sides in front of the insertion of the antennse, whereas in the 

 Carabidse it does not extend so far towards their sides as the insertion : 

 this will be perhaps better understood by comparing the shape of the 

 head of Cicindela as given in the accompanying woodcut with the shape 

 of the head of Pterostichus (Plate A, Fig. I.). ' 



In the Rhynchophora, as a rule, and in 

 other groups very rarely, the head is pro- 

 longed in front, so that the prolonged portion 

 is as long as the rest of the head, or even as 

 long as the whole body (as in Balanimis); 

 this prolongation is called the rostrum ; the 

 mandibles and maxilliB are situated at the 

 end of the rostrum, and not at its base, as 

 seems rather a common idea : the rostrum, 

 therefore, is a true portion of the head, and 

 in no sense a trunk ; on each side of the 

 rostrum there is usually a groove which 

 varies in size, and into which the insect 

 retracts the scape or long first joint of the 

 antennae when at rest : these are called 

 scrohes, and are very useful characters in the 

 determination of the Rhynchophora ; the 

 outer side of the mandibles is in some 

 families (e.g. the Carabidte) concave, form- 

 ing an elongate groove : these grooves are 

 called the mandihular scrohes. The anterior part of the head is called 

 the forehead or front, the central portion the vertex, and the posterior 

 portion the occiput ; as, however, the head is usually more or less sunk 

 in the thorax, and the occipiit more or less hidden, the whole portion 

 from the eyes to the front margni of the thorax is often roughly spoken 

 of as the vertex. 



a. Head of Cicindela (magnified) 

 with jaws closed, b. Ditto, with 

 jawsopen. I. Labrum. c. Clypeus. 



