THE STICK-INSECT. 178 



the Old World, and it has a wide distribution, occun-ing in Europe, 

 Africa, East Indies, Ceylon, Java, China, Sandwich Islands, 

 Australia, Island of Haraoa, and New Zealand." 



In the course of the present year several English collectors 

 have had in their possession specimens which were observed 

 to deposit their ova during the months of February, March, and 

 April, and the hatching of the ova began in the latter part of 

 June. It is highly probal)le that this insect, alien to the British 

 fauna, made its entrance into this country along witli fi-uit-cargoes 

 and nursery-stock imported from France. There is not much 

 chance of its becoming established here since, being accustomed 

 to mild temperatures, it fares rather badly under the changeable 

 conditions of the Eaglish climate. In captivity they require 

 close attention ; but by supplying them regularly with fresh 

 food-plants and by keeping the temperature of their surroundings 

 at about average house-temperature they appear to thrive. 

 Under these conditions they are quite healthy, and the mortality 

 is very low. 



Note on Parthenogenesis, 



A very curious phenomenon in connection with the repro- 

 duction of Bacillus rossii may be worthy of note. Although my 

 specimens were in the third generation reckoning from the first 

 generation in captivity, no male had been observed, and perhaps 

 parthenogenesis had been the normal method of reproduction 

 previous to this, as my observations wei'e necessarily limited by 

 the fact that I had no record of the generations preceding the 

 first one in captivity. Von Raehr (1907) records that in 1903 

 he received specimens of B. rossii which belonged at least to the 

 seventh parthenogenetic generation, being descendants of a half- 

 grown female captui-ed in Dalmatia in J 896, But the latter, he 

 says, may itself have arisen from an ovum parthenogenetically 

 produced, so that in all probability it was not the first in the 

 ancestral line to produce ova which had not been fertilised by 

 the sperm. 



These facts seem to lend guppoi't to the supposition that the 

 female of B. rossii can dispense with the male altogether and 

 that virgin, rather than sexual lepi'oduction is the normal 

 method adopted l)y thi« insect of perpetuating its race. We 

 cannot state with any degree of confidence why the insect has 

 betaken itself to the partlienogenetic production of eggs, but that 

 advantages accrue we are tolerably certain. In cases where, 

 owing to some cause or other, there is a scarpity of males, the 

 method would be a decided acquisition, since the great majority 

 of the more prevalent females would stand a very poor chance of 

 ever meeting a male and of the conse(iuent enjoyment of sexual 

 intercourse. 



I think that it is open to make the hypothesis that both sexes 

 of B. 7-ossii originally existed in equal numbers. Owing to some 

 cause with which we are not acquainted, the )nale,s began to 



