Contrihution to the life history of Orina tristis. 25 o 



the mesothorax partially or wholly disappears beneath the 

 prothorax, which may even slightly overlap the metathorax. 

 The 2nd thoracic segment is in these circumstances easily 

 overlooked, and owing to the backward direction of the 

 cox£e it is even difficult to believe that the 2nd and 3rd 

 pair of legs do not actually belong to the 3rd thoracic and 

 1st abdominal segments, taking each of these in fact for 

 the segment in front of it. 



The 7th abdominal segment is the last coloured like the 

 others, and has the appearance of a broad anal plate, the 

 8th is somewhat coloured, but is simple in structure and 

 retractile, the 9th and 10th are colourless and retractile, 

 the 9th forming a foot used in all progression. 



The hairs, which seem to disappear as the larva passes 

 to its later instars, do not in fact do so. On the contrary 

 they persist, though the larva grows however, they do not, 

 but maintain almost precisely the same size and distribu- 

 tion they had in the 1st instar. Their length in the 1st 

 instar is tolerably uniform all over the larva, viz. '25 to 

 '80 mm. in length. In the 2nd and 3rd instars they are 

 almost precisely the same, but of course make relatively a 

 much less show on these larger larvae. In the last instar 

 they remain of almost identically the same length on the 

 head, over the dorsum and posteriorly, but laterally they 

 have actually dwindled to a length of only from 0"06 to 

 0-20 mm. 



The hairs on the appendages and many of those on the 

 head appear like the ordinary tactile hairs terminating in 

 a solid sharp point, but the great majority, and nearly all 

 those on the general surface, are expanded at the tips, and 

 appear to be hollow, making the extremity trumpet-shaped, 

 but not so widely expanded perhaps as this suggests. 



The arrangement of the hairs may be described as 

 irregular, merely, no doubt, because it is too complex to 

 describe ; on the 2nd thoracic and following segments they 

 are placed on the summits of the two subsegmental ridges, 

 on 2nd thoracic almost in one row on each, on 3rd the row 

 on front ridge is a little irregular, on the back one they are 

 better described as in two rows. On the front ridges of 

 the 1st and 2nd abdominal they are in two rows, the hairs 

 in the rows alternating, they are more numerous on the 

 back ridges, whilst on both ridges of 5 and 6 they may be 

 described as in three or four rows, but in all cases without 



TRANS. ENT. SOC. LOND. 1903. — PART III. (OCT.) 18 



