134 FAMILY BOSTRYCHIDAE 



the end of April. It is not, however, the common bamboo beetle of 

 Calcutta, and was probably imported there in bamboos or other woody 

 material cut in the North of India forests during the preceding cold 

 weather. 



The life history of minntns in Calcutta was worked out at the Indian 

 Museum by myself between April and November 1903. The beetle and its 

 grub attack the internal woody structure of the bamboo in a manner similar 

 to that of pilifvons. D. niinntm, however, passes through a greater number of 

 generations in the }ear in the hotter moister climate of Bengal, the number 

 of life-cycles being from five to seven, the generations overlapping to some 

 extent. 



Both male and female beetles tunnel their way into the bamboo, and 

 after pairing the female lays its eggs in the interior, each beetle laying 

 about twent}'. From these eggs small white roundish dots of grubs issue 

 within a few days of their being deposited. These tiny larvae burrow 

 up and down in the interior of the bamboo, and reduce its structure to 

 powder. About four weeks are spent in this stage, and the grubs then 

 enlarge the ends of their burrows and change to pupae, which, after 

 some eight days or so, turn into the beetles. On becoming mature the 

 beetles bore their way out of the bamboos, and thus add further to the 

 tunnels already made in them. On emergence the insects fly off to attack 

 fresh bamboos, or they may bore into the one in which they have themselves 

 matured. There are thus three separate forms of attack : — 



(a) The female beetle bores into the interior of the bamboo and lays its 

 eggs there. This is the flrst attack on the bamboo. 



{b) From the eggs hatch out little grubs which feed upon the wood of 

 the interior of the bamboo, and thus undermine its strength. 



(c) The beetles on maturing from the grubs bore their way out of the 

 bamboo. 



The mature beetles issue either all from the same exit-hole or from one 

 or two only, these being often the former entrance-holes of the mother 

 beetles, which are considerably enlarged. Beetles of the new generation 

 appear also to make use of these old holes to enter the bamboo to egg-lay, 

 boring away from the old gallery when they have got inside. When bamboos 

 are in lengths it will be found that the beetles tunnel in them parallel to the 

 long axis and form galleries which open at one of the ends. The bamboo is 

 thus often completely hollow in parts without there being much outward 

 evidence of its having been badly attacked. This is more especially the case 

 when the beetles have entered and left by the same holes made at one of the 

 ends of the bamboo (cf. the lengths of bamboo shown in pi. ii). A feature 

 which greatly adds to the insect's power of doing serious damage is to be 

 found in the fact that in the warmer parts of the country it passes through 

 at least five, and perhaps more, generations or life-cycles in the year. It 



