270 FAMILY CERAMBYCIDAE 



at times covered with hair, the pubescence being often silky, and giving- 

 silvery reflections under the play of light ; or the hair may be in tufts on 

 them, with often additional tufts on the antennae, as in the case of the 

 brightly coloured diurnal Thysia wallichii (fig. 17). The female, in addition 

 to having shorter antennae than the male, has at times the pygidium exposed 

 below the apices of the elytra, and has a strong non-extruded ovipositor 

 for egg- laying, the egg being often put into deep crevices in the bark by 

 means of this instrument (cf. figs. 28, 29). 



The larva (fig. 30, c) is a stout, elongate, segmented, practically legless 



grub when full-grown, as shown in fig. 30, e, and is 



Larva. usually white, or yellowish white, or pale orange in 



colour; the segments taper only slightly from the anterior 



end downwards. Those we shall consider here are all wood-feeders, and have 



powerful black biting jaws or mandibles, with which they are capable of 



tunnelling down into the hardest timber. The grubs have short, four-jointed 



antennae, and may have very short legs in some cases. The upper surface 



of the head and of the thoracic segments is covered with a hard, horny 



plate ; the segments of the body have often tubercles on them, and the 



spiracles on the sides of the segments are well marked. 



The grubs spend their lives burrowing either in the bast and sapwood, 

 into the sapwood, or down into the heart-wood of trees, making galleries in 

 the latter which have a more or less square section. They may live for one 

 or more years feeding in this manner, or they may spend only a few months 

 or weeks in this stage of their lives. Before they change to the pupal state 

 they usually enlarge the end of their tunnel, and this enlargement may be 

 made in the bast layer in the sapwood, or the grub may bore down into 

 the heart-wood with the sole object of placing the pupal chamber there. 

 This latter procedure, as we shall see, is undertaken by several of our worst 

 cerambycid pests. 



The pupal stage is the resting stage, and during this period the insect 



gradually changes from the larval to the perfect or beetle 



Pupa' stage. The grub gradually takes on the appearance of 



the beetle, and when the pupa is fully formed we can 



see in it the shape of the future beetle with the antennae, legs, and wings 



pressed close down the sides and against the chest, all the parts being free 



and unenclosed in any silk covering or cocoon (fig. 31, c). In fact, the pupa 



usually lies quite naked in the pupal chamber at the end of the larval tunnel. 



In rare cases, of which we have a curious example in India in the beetle 



Ploccsderus obcsns, Gahan, the larva constructs a calcareous cocoon resembling 



a pigeon's egg, in which it transforms to the beetle state (see fig. 206). 



The actual change from the grub to the pupa would not seem to last, 

 in the case of the Indian forest Cerambycidae, for more than a few weeks, 

 and an examination of the pupal chamber will then disclose the fully formed 

 beetle with all its parts perfect. A superficial inspection will show that 



