100 D. d'emmerez de charmoy. 



In view of the number of the adult insects (40) met with at one time on a single 

 shrub of Cordia interrupta and the area over which they spread, it may safely be 

 concluded that there existed several hundreds of adult couples scattered over a surface 

 of about 400 to 500 arpents. This fact is a clear proof of the influence exercised by 

 a state of captivity upon the longevity and egg-laying power of certain species. 



At this stage, a question naturally arises which it would be difficult to answer for 

 the present. Granted that four couples were able to generate such a large number 

 of insects within a period of 8 months, and that these insects became scattered over 

 such a large area, how is it that in the same locality and under apparently similar 

 conditions a much greater number of couples could not, on two different occasions, 

 increase to a proportional extent ? At first sight one can only ascribe this to their 

 having been kept in captivity ; and with a view to investigating the different effects 

 that may be produced by such unnatural conditions, we shall here briefly review the 

 observations we were able to make both as regards Tiphia parallela and Elis rufa, a 

 species of Scoliid peculiar to the Mascarene Islands. 



It is known that captivity brings about a state of sterility in certain vertebrates, 

 and that this sterility may be temporary or permanent, according as certain conditions 

 are temporarily or permanently absent. Captivity entails restricted space, deficient 

 nest-material and, it may be, deficient food and unsuitable temperature ; and it may 

 well be responsible for the sterility and lesser vitality of certain animals. 



As regards Tiphia, climatic conditions may be excluded, as they were the same for 

 both captive and free insects ; nesting-materials may also be set aside, as they 

 consisted of Phytalus larvae, which in the Insectaries were available in greater 

 numbers and were of easier access. Insufficient space does not appear to be a check 

 on fertility, because from unfertilised (parthenogenetic) females that were kept in 

 such small vessels as flower-pots Nowell succeeded in obtaining fertile eggs. Further- 

 more, reproductions, although on a considerably reduced scale, actually took place 

 in Wardian cases and in the Insectary at Pamplemousses. It is possible, however, 

 that insufficient space, which necessarily impedes the movements of insects, coupled 

 with the absence of direct solar rays, may have a certain bearing on their longevity, if 

 not on their fertility. 



It will be seen further on that the egg-laying habits of Tiphia and Elis are such as 

 to necessitate a sufficient length of time to allow of all eggs being laid ; and it may be 

 as well to mention here certain facts which may somehow account for the considerably 

 reduced fertility of Tiphias when in a captive state. 



The writer of this article, whilst studying the life-history of Elis rufa, had been 

 struck by the invariable number of parasitised larvae or cocoons met with in 

 cane-stools infested by Lachnosterna. Whatever the number of larvae found 

 in a stool, there were hardly ever more than two — exceptionally three — para- 

 sitised larvae or cocoons to be found ; if larvae, they were of the same age ; if 

 cocoons, they hatched at a few days' interval. In captivity it was observed that 

 larvae were parasitised by twos and at intervals varying from 6 to 8 days. The same 

 observations were recorded in the case of Phytalus larvae parasitised in open fields by 

 Tiphia. 



Examinations of the ovaries of several female Elis showed that the eggs could only 



