﻿MICKO-OKGANISMS BY FLIES IN SAINT LUCIA. 



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One characteristic of the larvae of these six flies, which is of considerable 

 importance, is that they all attempt to get well away from their breeding ground 

 to pupate in the bush, or under stones and other objects in the neighbourhood. 

 The larva of Limosina punctipennis possesses the " hold and let go " mechanism 

 for this purpose, so that by uniting its head and tail ends and then abruptly 

 straightening itself out, it is able to hurl itself well clear of its breeding ground. 



The following table summarises a few points observed in connection with the 

 six species under consideration. 





No. of times found 



Egg or larva 



Larval 



Pupal 





in 25 inspections. 



deposited. 



period. 



period. 



Sarcofihagula sp. 



24 



larva 



3-5 days 



5-7 days 



Sarcophc/ga sp. 



18 



larva 



5-7 days 



6-9 days 



Sarcophaga aurifinis ... 



22 



larva 



8-11 days 



10-13 days 



Sepsis sp. 



25 



egg 



3-4 days 



2-4 days 



Drosophila melanogaster 



1 



egg 



2-3 days 



3-5 days 



Limosina punctipennis . . . 



25 



egg 



2-4 days 



2-5 days 



The undetermined Sarcophaga and the Drosophila are frequently found upon 

 food, and the others, with the exception of the Sepsis, have occasionally been found 

 upon provisions in houses. They are all of them liable to infect water supplies, 

 especially in dry weather. 



Experiments to elucidate the relations of larvae and pupae of the flies 

 to micro-organisms. 



Experiment I. 



(a.) Twelve larvae of the Sarcophagula, which had just left faecal matter to 

 find a protected situation in which to pupate, were placed in a sterile vessel for 

 two hours to allow digestion and natural cleaning processes to proceed. They 

 were now each in turn seized with forceps and the two ends snipped off with 

 sterile scissors ; these cut surfaces were now burnt with a hot needle to sterilize 

 them, and a serrated platinum needle was passed through one of these burnt 

 ends, the interior of the maggot being removed and transferred to five cubic 

 centimetres of sterile peptone broth. This was then ground up with a glass rod 

 and a number of plate cultures were taken from a definite quantity of the pre- 

 paration. In the 12 cases the number of micro-organisms which grew as colonies 

 varied, but not more than 31 per cent, from the two middle numbers. The total 

 number of colonies for the twelve maggots were reduced to the number 100. 



(b.) Twelve pupae approximately 24 hours old were taken and similarly treated 

 as the larvae in (a.). The numbers of their colonies were compared with the 

 numbers in (a.) and gave 26 per cent. 



(c.) Twelve pupae approximately 48 hours old were then taken and gave five 

 per cent, of (a.). 



(d.) Twelve pupae approximately four days old gave a result of less than 

 0*4 per cent. 



23527 F 2 



