tion goes there are very many more larvae than can be pro- 

 vided for by such means, and we are almost forced to con- 

 clude that there is some other way for them to get food. This 

 might be accomplished by swallowing the oil and digesting 

 the available food material. Crawford states that it is plain 

 that tliis is "the only way" for the animals to get nutriment. 

 I cannot state from observation that tlie maggots take oil into 

 the digestive tract. If they do, it is likely that they would 

 ingest some organic material, possibly juices derived from oil- 

 soaked plants or animals. C'raAvford suggests the probability 

 of the paraffine base of the natural oil serving as food. 



I have reared pupae and imagos from larvae that were 

 kept in freshly pumped oil and in that passed through a Gooch 

 filter. Oil as" it issues from the pump probably does not con- 

 tain any foreign particles, nor extracted organic juices. The 

 filtered oil will doubtless be free from bits of organic matter, ■ 

 l)ut not from organic juices if these are present at all. The 

 fact that larvae act normally in such media and undergo their 

 normal development does not, however, clear matters greatly. 

 The larvae experimented on may have been so old that they 

 would have pupated without further feeding, or they may 

 have posessed sufficient stored food to carry them through. 

 If larvae, kept from the very first in filtered or fresh-pumped 

 oil, were to pupate and produce adults, it could reasonably 

 be claimed that they eat the oil or get food from it in some 

 other way. The interest in this question makes it deserving 

 of careful study. 



Crawford tells of keeping four larvae in a mixture of 

 petroleum and a consideral)le amount of white arsenic. One 

 maggot died in three days, the others lived for four days. 

 The experimenter feels that this shows the resistance of the 

 digestive epithelium to poisons, but it is to be suggested that 

 it may show equally well that the arsenated oil was not eaten, 

 though Crawford states that the animals "swam and fed" 

 as in pure oil. The same investigator kept larvae for four or 

 five days in mixtures of petroleum and such substances as 

 clove oil, b/enzine, cedar oil and turpentine. He found that 

 there was no ill effect so long as the mixture was tliick enough 

 to support the animals and keep the spiracles above the sur- 

 face. This opens the possibility of keeping maggots in media 

 like syrup or gum arabic solution, in the endeavor to dis- 

 cover whether petroleum is necessary for the life of these 

 animals. If they should go through a normal development in 

 syrup, for example, it would show pretty conclusively that 

 they do not have to eat the oil to live. 



The pupae are always formed outside the oil so far as 

 I liavp been able to determine. Dead maggots can lie ol)tained 

 by washing repeatedly, in kerosene, oil that had contained 

 larvae. I have never obtained a i)upa-case in this way, but 

 the larvae die in large numbers as is shown by the remains 



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