VOL. XXn.] PHILOSOPHICAL TRANSACTIONS. 517 



tier they insinuated their tail into the bodies of the worms ; and this the flies 

 did in a short time to all the worms they came near ; but what was most 

 remarkable in this action was, that in this conjunction they never touched the 

 lice, either with their feet or bodies, being much too large to approach them ; 

 and as they entered the bodies of the lice they made a trilling motion or shaking 

 with their tail, that they might thrust it in the farther. 



Now as the flies remained but two days alive without copulation, whereas 

 the green lice lived seven or eight days, I thought the flies by that insinuation 

 of their tails into the bodies of the lice, they conveyed their eggs in at the 

 same time, and that from those eggs young worms should have been produced, 

 which having received their nourishment and increase from the bodies of the 

 lice, should be changed again into a fly, but the green lice died, and for the 

 most part dried away. 



Not content with this observation, I collected 25 dead lice, all of which had 

 in their bellies a worm, or else a fly newly changed, for I saw through the skin 

 of some of the lice, living flies, which flies I took out alive from the bodies 

 of some of those green lice. Having shut up these lice in a clean glass tube, 

 and some days after the fly coming out of them, I went into the garden to get 

 four caterpillars or riper worms, amongst which there was one that was very 

 hairy, and I observed that when one of the flies approached this hairy ripe 

 worm, to thrust his tail into him, as soon as he touched the hair, he suddenly 

 drew it back again. 



I put also into the glass tube, together with the worms or creeping insects, 

 three aurelise cases or popkins, which had lain in their web in some withered 

 leaves, with the intent that the flies should insinuate their eggs into the bodies 

 of the worms, and that so doing, there might proceed from the body of each 

 one 25 flies ; but they did not succeed with me, because, as I imagined, all the 

 flies, though six or eight of them together were running and flying about the 

 glass tube, died away without laying eggs, which I judged, was only because 

 they wanted food, for we see that there are some flies that lay eggs without 

 eating, and then die, whereas others shall lay no eggs unless they eat. 



Now if we observe the wonderful formation of such a small creature, and 

 how such a fly is produced, and then consider that the worm which is changed 

 into the fly, and we imagine that such a thing will not happen, unless the worm 

 that comes out of the egg of the fly, makes use of another creature for its 

 food, we must remain perfectly amazed. Further, I saw many dead creatures 

 lie about in the tube from whence no flies were produced, and from whence I 

 did not imagine that any flies would come, believing I had not handled them 

 tenderly enough, and that therefore they were dead ; but about a fortnight after 



