Insects. 531 



E. T. S. seems not to have observed the dung fly's being 

 affixed by its proboscis only, as Mr. Thompson has. In 

 Kirby and Spence's Introd. (ed. 1826), iv. 203., mention is 

 made of " several specimens of a fly related to Eiimerus 

 pipiens Meig." which, dead, adhered by their proboscis to a 

 panicle of grass. I know of one fact, which may or may not 

 have a relation to the explanation of this : — Among the flies 

 which I have noticed above (p. 527.)? as abounding dead upon 

 the bark of the ehn trees, I noticed, at two different times, 

 two live flies (it might, possibly, be one seen twice), whose 

 condition may afford some relevance of this question : per- 

 haps, however, none at all. Though alive, they seemed in 

 an incipiently morbid state ; but were capable of flying off 

 when approached very close. At the tip of the proboscis of 

 each, there was a globule of transparent whitish fluid ; the 

 globule was not larger than the head of a pin, and appeared, 

 disappeared, and reappeared at least once, perhaps more. I 

 leave this fact without an attempt to account for it; but have 

 cited it, in the thought that cases may happen where this 

 regurgitated fluid may, in the fly's dying, and the proboscis 

 falling into contact with an object, gum it to that object. It 

 is, however, right to state, that, in the countless instances of 

 flies dead in the posture of life, adhering to the surface of the 

 bark of the elms, I did not see one attached by its proboscis 

 only ; and, I think, not one with its proboscis attached at all. 

 They all rested upon their legs and upon the terminal half of 

 their abdomen, which was, in some degree, and by some 

 means, affixed to the bark ; and, in cases not a few, plainly 

 by means of a whitish matter that seemed to have erupted 

 from the last few rings of the body on the ventral surface. 

 Fibres of mould seemed, in some cases, to have farther 

 affixed the abdomen to the bark ; and the dorsal surface of 

 the posterior part of the abdomen wore, at least, in some 

 points of light, a glaucous hue. In other dead flies, in a 

 more advanced state of decay, increased degrees of whiteness 

 were obvious ; produced either from an increase in the quan- 

 tity of mould or of the erupted matter : and this was accom- 

 panied by some distortion of the component parts of the fly, 

 which were enlarged, and made to seem farther asunder and 

 less compactly connected. See farther in p. 527. 



In the latter part of 1833, Mr. Fennell sent us two flies, 

 found dead, I think in the posture of life, upon a plant; and 

 these, Mr. Westwood informed us, were individuals " of a 

 species of Anthomyia ; " and that they had " died of the 

 disease which Messrs. Kirby and Spence call plethora. (In- 

 trod, fed. 1826], iv. 202.) The circumstance is of verycom- 



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