npn 



10 1900 



1^ 



JOURNAL OF VARIATION. 



Vol. XII. No. 11. November 15th, 1900. 



Photographing the eggs of L^pldopUYSi {n-ith plate). 



By F. NOAD CLAEK. 



The illustrations of lepidopterous ova exhibited in Plate XI have 

 been reproduced from photographs made with the microscope from" 

 freshly-laid specimens, kindly supplied me by Messrs. Prideaux,: 

 Montgomery, Tutt, and Dr. Chapman, to whom I am much indebted. 

 Those of the Lyctenids lend themselves admirably to photography, 

 in that they are of. small size, and the surface markings are more 

 or less in one plane of focus. The spherical surface of the larger 

 ova renders photography more diffictilt, and in some cases, such as the 

 Argynnids and larger moths, almost impossible. 



Under casual observation, the several species of Lycsenids appear 

 to present but little difference from each other, but careful examination 

 will show that really marked differences exist in most of the species. 

 This is especially noticeable between those of Polyommatus icarus and 

 P. bellarijUH, Nnniiades semiartjits, Callophnjs ruhi, &c. 



The method of photographing these eggs is comparatively simple. 

 The ultimate result is much enhanced if the ova are mounted in a 

 suitable manner ; for instance — a white egg should have a dark back- 

 ground, and vice verm. Whenever possible, the egg should be photo- 

 graphed in situ, that is, as laid in the natural state, either on leaf, bud,- 

 or flower calyx, &c. In some of the examples illustrated they have' 

 been detached from their natural support, and, for the sake of contrast, 

 placed on a spot of asphalt varnish. It is absolutely necessary that the 

 eggs should be photographed in a plane exactly at right angles to the 

 axis of the microscope, otherwise some of the eggs (if in a group) will 

 certainly be out of focus, and consequently blurred in outline. ' 



The objective I use is a 2-inch, and I make it an invariable rule to ■ 

 photograph all ova at precisely the same magnification, so that the 

 results will give a correct idea of their relative size. Thus, the egg of 

 Ciqmlo minima is seen to be the smallest of the genus in actual size, as 

 its name implies. Illumination is effected by means of an ordinary 

 bull's-eye condenser, focussing obliquely the light from a good paraffin ' 

 lamp. Exposure of the plate varies from one-half to two minutes. 



Until a lens is invented which will give an image of a spherical ■ 

 object, representing more than one plane of focus, we shall have to be 

 content with the present capabilities of micro-objectives. The obtaining 

 of this, I fear, is far distant, but at any rate photo-micrography in its 

 present state of perfection, gives us a correct and satisfactory means' of 



