58 INDIAN FOREST INSECTS 



scutellum. Occasionally the elytra leave a few of the posterior segments 

 of the body visible, which are known as the pygidium. The elytra are 

 always present in beetles, even in cases where there are no lower wings to 

 protect (as e.g. in the longicorn Teledapus, p. 280). In the latter case 

 they are often joined together down the central suture and are immovable. 

 This central suture, however, is always perceivable. When the beetle 

 wishes to fly, the elytra part down the suture and open out laterally and 

 upwards to allow of the lower wings being expanded. In some instances, as 

 in the rose-chafers (p. 91), the elytra are joined together in this way though 

 under-wings are present, and they are then raised as one piece to permit the 

 lower wings to be expanded when the beetle takes wing. The elytra are 

 occasionally sculptured in curious fashion, and may have bunches of hairs 

 protruding in parts as in the case of Thysia wallichii (fig. 17). The second 

 pair of wings when not used in flight are folded up beneath the elytra. 

 They are membranous and set with well-marked nervures or veins which are 

 broken across at certain points to permit of the wings being folded up when 

 the insect is not on the wing. These veins are used in some instances in 

 classification. 



In the legs three to five visible tarsal joints are present, and some of 

 these joints may be bilobed. The tarsi are set with a spongy felt-work 

 of hair which enables the insects to walk about on bark, plants, etc. The 

 last tarsal joint ends in a pair of claws. In the abdomen five to six seg- 

 ments are visible on the ventral surface. 



There is often a considerable difference in the appearance of the two 

 sexes in the Coleoptera. The females are sometimes larger than the males, 

 and the antennae in the male may be much longer than in the female, or 

 the tarsi may vary in size, or the number of tarsal joints may vary in 

 the two. Individuals of the same species also vary very greatly in size, 

 as is shown in the four individuals of the longicorn beetle Hoplocerambyx 

 spinicornis, shown in fig. 32. 



Some beetles are capable of producing sound by having parts of their 

 structure set with file-like processes which are rubbed over one another. 

 The result produced is a squeaking noise ; several Cerambycidae produce 

 sounds of this nature, such as Hoplocerambyx, Molesthes, etc. 



In the glow-worms and fire-flies, which are beetles, light is produced by 

 the oxidation of proteid matter in the abdomen. 



The eggs of beetles are in forest forms mostly soft globular or elliptical 

 bodies, semi-translucent or opaque white. These may be deposited in 

 crevices in the bark, or the beetle tunnels into the tree and deposits them 

 in prepared receptacles in the bast or wood. In the cases where the eggs 

 are laid in the open they are hard externally, and usually whitish or greyish 

 in colour. 



The larva is grub-like, having a distinct head and jaws. It is sometimes 

 furnished with antennae, and may have three pairs of feet on the front portion 

 of the body. The different families vary in this respect, however, as shown 



