FAMILY BOSTRYCHIDAE i 35 



has been shown that the insect lays about twenty eggs, and therefore one 

 female beetle may produce the following progeny in the year, on the 

 supposition that only five generations are passed through : 



One Female Beetle. 



ist generation ... i X 20 : 20 beetles, say half males and 



half females (the latter are, 

 however, usually in excess 

 of former). 



2nd 10 X 20 : 200 beetles, say half males and 



half females. 



3rd ... 100 X 20 = 2,000 



4th ... 1,000 X 20 : 20,000 



$th ... 10,000 X 20 = 200,000 



If there is a sixth generation the number <pf females increases to 

 2,000,000. 



Taking only 50 per cent, of the fifth generation beetles as maturing and 

 laying eggs, we still have 100,000 insects as the progeny of the one 

 mother beetle in the spring. This great prolificness easily explains why 

 bamboos suffer so greatly from the shot-borer's attacks throughout the 

 country. 



The result of my observations in Calcutta showed me that at least five 

 generations of the beetles issued between the last week in April and the end 

 of October as follows : 



The first taking about seven weeks, from end of April to the third week 

 in June, to run through all its stages ; the second about four to rive weeks, 

 from the third week in June to near the end of July; the third four weeks, 

 from the end of July to the beginning of September; the fourth less than 

 four weeks, from first week in September to end of the month; the fifth 

 from end of September to end of October. It is probable that many of the 

 beetles of this generation were caught and killed off by the cold snap 

 experienced towards the end of the month. 



I have detailed at length in three pamphlets * dealing with this bamboo- 

 borer the series of experiments carried out by myself at the Indian 

 Museum, Calcutta, during my tenure of the Superintendentship of that 

 Institution in 1903. As described in the monographs in question my i-\|>rn- 

 ments were inaugurated to enable me to advise the Superintendent of the 

 Government Telegraph Workshops (Mr. Williams as to the economic value 

 of experiments he was conducting with a view to protecting from tin- 

 attacks of the beetle bamboos which he; was converting into |.o|,> 



* (i) A Note on the Preservation of llamboos from the Attacks ot tin- iLiinln... ! 

 Shot-borer, App. Series liul. Forester, xxix, no. 12 (1903) : 2 lliid. JIM! edition-, - and 



enlarged, Forest Pamphlet no. 15, Supt. Govt. Printing, ('alnm.i [91 -, A I imliri Note 



on the Preservation of Bamboos from the Attacks of tin- l;;unl>oo l',r< tl< 01 sha-1 mid. /;/,/. 

 Forester, vol. xxxi, p. 249 (1905). 



