70 SPOLIA ZKYLANIL'A. 



until the latter have caught them up and made their exit. The 

 adult wasp completely frees itself from the pupal skin, and 

 expands its wings while still within the cocoon, and then waits 

 patientlj' for its turn. The larva is at first of a pale greenish 

 colour. It darkens as it increases in size, and when fully grown 

 is of a dull greenish black tint with numerous white specks. 

 The form of the cocoon is worthy of notice. Near the lower 

 extremity there is a distinct constriction. The pupa rests in the 

 upper part, while the lower part receives the excreta which are 

 evacuated — once for all — immediately before pupation. The adult 

 insect (tig. 2a), as described by Bingham, loc. cit., is "Black, with 

 glittering silvery pile ; the second and third abdominal segments 

 red, shaded with fuscous above ; legs testaceous, variegated with 

 black ; wings hyaline and iridescent ; nervures and tegulse pale 

 testaceous." 



Another tube-inhabiting insect \sStigmus niger, Motsch.* The 

 wasp does not utilize ready-made tubes, but constructs them by 

 drilling out the pith from a grass stem or the slender twig 

 of some plant. It generally selects a dead twig for the purpose. 

 Fig. 1 shows a nest constructed in the pith of the "Mana grass ' 

 {Andropogun nardas), a very favourite site. The tunnel is often 

 carried down for a considerable distance, perhaps 10 to 12 inches* 

 the cells being disposed at the far end. Stignms niger provisions 

 its cells with Aphides, and must destroy a great number of these 

 little pests. The partitions are formed of pulped pith. The fully 

 grown larva has the anterior and posterior extremities pale 

 yellowish, the median segments blackish green mottled with pale 

 spots. Just before pupating the larva voids the contents of the 

 alimentary canal and assumes a uniform orange-yellow colour. 

 The pupa is naked. It is at first orange, with eyes and ocelli 

 brown. As development advances it gradually becomes blackish. 

 Only two species of Stigmus occur in the Indian region, S. con- 

 gruus, Walk., and S. niger. Both species are found in Ceylon. 



Royal Botanic Gardens, 

 Peradeniya, September, 1903. 



* Stigmus niger, Motsch. Bull. Soc. Nat. Mosc, 1863, p. 23. Bingham, Faun. 

 Brit. Ind., Hymenoptera, vol. I., p. 267. 



