HARDWICKE'S SCIENCE-GOSSIP. 



29 



entire suppression of one or more parts and by the 

 multiplication or enlargement of others it is easy to 

 produce the most divergent forms met with. 



This fact, however, only establishes itself in the 

 mind after much investigation, but I venture to think 

 that a well-selected set of slides of the "teeth of 

 flies " would form as good an illustration of the 

 development of an organ as it is possible to find 

 within the scope of animal economy. 



Although not immediately connected with the 

 main subject of these notes, there are one or two 

 ideas which have been suggested during the investi- 

 gation which I venture to add. 



At first sight the Diptera would appear to offer 

 little opportunity for studying traits of character, yet 

 I dare affirm if anyone will give the requisite atten- 

 tion to the matter he will not be long before he dis- 



Scctlc of 1000'" of tin t/irh 

 Fig. 10. — Teeth of Cordylura ptibera. 



covers peculiarities of which he had little prior 

 conception. There are social flies, and solitary flies ; 

 flies which show an innate smartness in their move- 

 ments, and others sluggish and indolent in their 

 avocations ; timid flies, persistent flies, pugnacious 

 flies, cunning flies, patient flies ; in brief, whether 

 these habits are ascribed to instinct or reason, taking 

 into account the services they perform they are as 

 well provided for their proper discharge as any other 

 class of animals occupying a higher position in the 

 scale of the great scheme of nature, and their recog- 

 nition adds another point of interest for those who 

 take up the study of the Diptera. 



Among the Syrphidse, which are truly flower-loving 

 flies, no trace of dental organs can be discovered, the 

 development of pseudo-trachece, however, reaches its 

 maximum proportions in both size and number, so 

 large, indeed, are the canals formed by them that 



pollen of plants can be conveyed in an unbroken 

 condition to the stomach ; I have a slide before me 

 as I write, showing the stomach of one of these flies 

 quite distended with grains in all stages of decom- 

 position. The bulk of these flies are doubtless 

 nectar-loving creatures in their perfect state, and in 

 all their stages may be looked upon as friends to the 

 gardener, the larvae feeding upon aphides, while the 

 fly aids the fertilization of the plant. 



The phenomenon of sleep may be frequently 

 witnessed in this family of flies. I have often seen a 

 fly alight upon a leaf, and in the space of a few 

 seconds become perfectly motionless, and in a few 

 more seconds lose all consciousness of external 

 objects; the hand could then be approached, or a 

 feather, or any other object, could be waved about 

 within a tenth of an inch of its large eyes, but it 

 would remain perfectly oblivious of any 

 danger. Repose of this kind rarely 

 exceeds a few minutes at a time during 

 the day-time. In the higher animals 

 sleep is supposed to be the result of a 

 torpid condition of the brain, during 

 which its volume is somewhat di- 

 minished in consequence of a less active 

 state of the blood passing through the 

 vessels of the brain ; exercise or mental 

 occupation produces sleep, provided 

 they are judiciously indulged in ; as 

 these flies are almost constantly on the 

 wing, hovering hawk-like over plants, 

 their attention apparently riveted upon 

 the object they are seeking, there must 

 be a large expenditure of muscular 

 force and (if they think) the mental 

 energy which requires frequent recruit- 

 ing by short periods of repose. 



Occasionally accounts appear in the 



newspapers of deaths having occurred 



from the bite of a fly. At first sight 



one is almost tempted to be increduloui 



as to this being the true cause of such fatal results. 



During the investigations necessary for compiling 

 the series of notes on the teeth of flies, I have made 

 some thousands of dissections of the mouth organs of 

 various creatures of this large order. It is not at all 

 an unusual occurrence to find the oral aperture 

 literally teeming with Bacteria. Is it possible that in 

 certain conditions of the blood, the bite of a fly, so 

 infected, may be followed by a fatal result ? If so, 

 surely it is not too much to inquire if medical science 

 cannot speedily find an antidote. 



There may be nothing novel in this information, 

 but at any rate, so long as death may be attributed 

 to such an apparently simple cause, nothing bearing 

 on the question ought to be considered unworthy of 

 investigation, and it is with this object I am placing on 

 record the experience gained over a number of years 

 of close attention bestowed upon these insects. 



