AT THE MICROSCOPE. Ill 



{Pediculus, Phthirius, ffcemafopiftus), with the Hemiptera. This 

 was a decided step forward, but a more complete knowledge of 

 the principles of classification shows that it should be considered 

 only as a provisional one. 



I have compared the specimen marked F. vestimenti with 

 authentic specimens, and though I would not like to speak too 

 positively, since preparation with potash and pressure alter appear- 

 ances so much, my belief is quite that it is a specimen of P. 

 capitis^ $ . 



Bibio Marci, ? (PI. 24, Figs. 1—4).— In examining 

 the specimen labelled " Fly," to endeavour to make out what it is, 

 we look first for the " halteres " (" balancers ") ; finding them, we 

 are assured that it is really a Dipteron before us. The appearance 

 of the wings is such that at first we really felt inclined to suppose 

 it an Hemipteron. Having ascertained so much, the antennas are 

 examined. These are found to be composed of nine joints, 

 cylindric perfoliated. It cannot, then, be a Gad-fly, but must 

 be one of the TipulidcE, a familiar example of which is the 

 " Daddy Long-legs:' The having the " fore-thighs thickened " is a 

 character of the genus Bibio ; in the sub-family Bibionides^ the 

 presence of the four-jointed palpi confirms this, and the neuration 

 of the wings, in so far as can be made out, renders it probable that 

 we are looking at a female of Bibio Marci. I do not know the 

 habits of the creature sufficiently to be able to explain the purpose 

 of the incrassated anterior femora and strong-spurred tibiae. 

 Walker's Diptera Brita?inica will be the best book to search for all 

 that is known about it. There is a remarkable disparity in the 

 appearance of the sexes in this genus; on the 15th of this month, 

 scores of paired examples were to be found about here. This had 

 been preceded by the appearance of great numbers of the males, 

 with but here and there a female. This sight was only for a very 

 brief period ; now they have entirely disappeared, and I cannot 

 procure a single example. An entomological friend tells me they 

 only appear when the sun is shining at its brightest, and that with 

 even a passing cloud they disappear entirely. The kidney-shaped 

 spiracle is unusual. The Gad-flies have also a tri-lobed pulvillus, 

 but the mouth shows at once that it cannot belong to that genus. 

 I cannot here see a trace even of the " pseudo-tracheae" so charac- 

 teristic of the Dipterous proboscis. For comparison, I also give 

 details of mouth of Gad-fly (PI. 29, Fig. 5). A comparison 

 of these with the structures found in Bibio Marci will illustrate 

 the remarks made on the subject, and render further description 

 unnecessary. 



