THE 



MONTHLY MICROSCOPICAL JOURNAL. 



JUNE 1, 1876. 



I. — Oil the Markings of the Body-scale of the English Gnat and 



the American Mosquito. 



By Dr. J. J. Woodward, U. S. Army. 



(Read be/ore the Royal Microscopical Society, May 3, 1876.) 



Platks CXXXIX. and OXL. 



My attention was first directed to the markings on the body-scales 

 of the English gnat by a letter received last summer from Mr. John 

 Mayall, jun., enclosing a mounted slide of these scales, and a photo- 

 graph of a drawing of one of them by Dr. John Anthony, of Bir- 

 mingham, representing the scale as marked hy longitudinal headed 

 ribs, having three uniform imrallel roivs of smaller heads in every 

 interspace hetween two adjoining ribs. (See Pi. OXXXIX.) 



Mr. Mayall stated that Dr. Anthony had made the drawing to 

 represent an appearance of the scale glimpsed by central light, but 

 had not been able to show this appearance to him in the microscope 

 as definitely as it appears in the drawing, and requested me to 

 undertake to photograph the scale as seen under the microscope. 

 This I did at such leisure hours as I was able to command during 

 the latter part of last year, and in so doing arrived at results which 

 may perhaps be of interest to some of your Fellows. 



I at once observed the very great similarity between the scales 

 of the English gnat and those of the American mosquito, with 

 which I had been familiar for a number of years ; a similarity 

 which relates to all the details of surface markings, as well as 

 to the size and general outhnes of the scales. In the case of the 

 mosquito, I had seen that the scales are crossed transversely by fine 

 markings, probably ridge-like corrugations of the thin double mem- 

 brane composing them, and that these transverse markings crossing 

 the longitudinal ribs at regular intervals, gave to the latter a beaded 

 appearance; but I had not believed that the transverse markings 

 were also beaded. I must add that the ribs and transverse mark- 

 ings exist on both surfaces of the scale, though much more boldly 

 on one than on the other, and that the longitudinal ribs of the 

 opposite sides unite at the broad end of the scale, where they 

 generally project as bristle-like appendages beyond the general 

 contour. 



My examination of the shde received from Mr. Mayall has led 



VOL. XV. T 



