April 29, 1892.] 



SCIENCE. 



245 



3. The mouth parts are developed for sucking only. 



4. The attachment of the abdomen to the thorax in some 

 flies shows that they once possessed a pedunculated abdomen, 

 similar to that of Hymenoptera (p. 251). 



Of these features, the first is the most weighty. Had not 

 its importance been overlooked, the order could never have 

 been thought inferior to the Lepidoptera, of which the mem- 

 bers have while larvae thoracic legs and usually abdominal 

 ones also. Among the Hymenoptera, the Tenthredinidas 

 have thoracic legs and even more numerous abdominal ones 

 than the Lepidoptera. The Uroceridse also have rudimen- 

 tary thoracic legs, although the larvse are borers in wood. 



The second and third arguments are essentially one in 

 ■principle. In the lower winged insects, we find both pairs 

 of wings of equal size and importance. The Hymenoptera 

 show a condition in which the hind wings are much smaller 

 and so of less use. Now, why do not the Diptera represent 

 the extreme of this series ? The question is not whether two 

 pairs of wings or one pair are in themselves " higher; " it is 

 rather, Which type shows the greater departure from the 

 forms universally acknowledged as ancestral ? So regarding 

 the mouth development: If the mandibular mouth of Thy- 

 sanura, Odonata, etc., be admitted as representing the ances- 

 tral form, then surely the mouth combining mandibular and 

 suctorial apparatus is intermediate, and that with only suc- 

 torial organs is the ultimate degree of specialization. The 

 recent researches of Dr. John B. Smith (Trans. Am. Ent. 

 Soc, XVII.) show that true mandibles are almost never 

 present in Diptera (he found them only in Simulium). Al- 

 though his conclusions in this respect, as well as in regard 

 to the homologies of the dipterous mouth in general, are 

 •widely different from those of earlier investigators, they are 

 probably correct. In summing up, he says (p. 339), "The 

 development required is simply a further development of the 

 line started in the Hymenoptera." 



An argument that strongly reinforces the first one above 

 is found in the fact that the embryo in Diptera, at least in 

 the higher forms, does not develop any traces of legs, differ- 

 ing in this respect from even the highest Hymenoptera, which 

 first develop the legs and then reabsorb them before batching 

 ^{Psyche, June, 1891, p. 98). 



The subject of mimicry also throws some light on these 

 relations. As is well known, the Diptera afford many in- 

 teresting cases of mimicry, and it is important to our theory 

 to notice that they generally imitate the Hymenoptera, es- 

 pecially the very highest forms, such as wasps, humble-bees, 

 and even honey-bees. One of the most widespread of all 

 species, Eristalis tenax Linn., is such a good imitation of 

 the honey-bee as to deceive the very elect. One of my stu- 

 dents, an enthusiastic collector and well acquainted with this 

 case of mimicry, once grasped a bee in his liand, under the 

 impression that he was capturing one of these flies. Now, 

 on any theory, we must admit that these species of flies are 

 -of more recent origin than the species which they mimic. 

 Most of these imitative flies belong to the family Syrphida;, 

 which is considered to be one of the oldest of the group 

 Cyclorrhapha, comprising the higher flies. 



The Diptera, as a whole, are wonderfully rich in peculiar 

 modifications of structure. In almost any organ the variety 

 of forms exceeds that of any other order. Even the antennae 

 of beetles do not surpass, if they equal, those of flies in this 

 respect. The wings are far more variable in venation than 

 those of any other order. The variety and complexity of 

 organs for grasping the female are almost beyond belief to 

 £)ue who has not seen them. 



The one thing which has prevented the recognition of the 

 real rank of the Diptera is a lingering notion that specializa- 

 tion by reduction really brings an insect down to a lower 

 position in the scale. The word "high" suggests the idea 

 of "complete," or "perfect," or "typical." If Professor 

 Hyatt's test were to exclude every other, as it ought to, there 

 could scarcelj' be any further disagreement on the question 

 of the highest order. 



The line of argument here suggested points to the Pupi- 

 para as the highest of all insects; nor would I in the least 

 seek to evade the conclusion. Of the group, I have seen 

 only the Hippoboscidae ; among these the sheep tick, Melo- 

 phagus ovinus Linn, appears to deserve the highest rank. 



J. M. Aldeich. 



DEBLOOMING MINERAL OILS. 



It is a common practice with dealers in mineral lubricating 

 oils and what are known as wool-slock and neutral oils to 

 add certain chemicals to these oils to destroy the bluish fluor- 

 escence or "bloom." The bloom on ordinary refined kero- 

 sene is very noticeable, while paraffin oil, i.e., oil that has 

 been distilled from petroleum tar, or residuum, is intensely 

 blue. A good way to see the bloom of an oil is to view it 

 through the ordinary four-ounce sample bottle. These bot- 

 tles are made with straight sides and of white glass. A 

 test-tube answers very well. The bottle should be held in 

 front of a window and viewed through the bottom. 



If a drop of oil be put on a piece of black glass, or on a 

 piece of window-glass painted black on the bottom, the bloom 

 will show even when the oil appears bloomless in the bottle. 

 The bloom of oils may be destroyed or masked by nitric acid, 

 nitro-benzol, di-nitro-naphthalene, and some other nitro- 

 compounds. The use of nitric acid, of course, destroys the 

 oil for lubricating purposes. 



The di-nitro-naphthalene of commerce is a very efficient 

 deblooming agent. I found, however, that if this material 

 be washed in hot water until the free acid and free nitro- 

 benzol (?) be vrashed out, it loses its deblooming properties. 



A small percentage of oil of myrbane added to wool-oil or 

 neutral oil will destroy or mask the bloom altogether. At 

 the same time it, like the di-nitro-naphthalene, darkens the 

 oil, and gives it the odor of benzol. 



The usual practice is to add a quantity of di-nitro-naphtha- 

 lene to a portion of the oil to be treated, warming it gently 

 meanwhile, and then, when the oil is about to be sold, to 

 add this strong solution to the bulk of the oil. This is done 

 because the nitro compound is liable to crystallize out in the 

 cold, and also to stain yellow the containing vessel and to 

 darken the oil on standing. 



If a bright piece of steel be put into oil containing much 

 di-nitro-naphthalene the steel becomes corroded. It will be 

 readily seen that such oil is unfit for lubricating purposes. 

 If the oil be filtered while cold, fine crystals of di-nitro-naph- 

 thalene will collect on the filter, and at the same time the 

 filter is stained yellow. The bloom reappears in the filtered 

 oil, showing that the bloom was only covered up and not 

 destroyed. 



The only safe and proper way to bleach and debloom oil 

 is to expose it to the sun and air for a long time — two or 

 three weeks or so — depending on the weather. By this 

 method no deleterious substances are added to the oil, while 

 at the same time it is rendered sweeter in odor and the 

 " body" is somewhat inci'eased. The bleacher consists of a 

 shallow tank, sometimes covered with glass, but more gen- 

 erally exposed to the sun and rain. Into these tanks a few 



