500 
DIOPTIDAE. General Topics by Dr. A. Seitz. 
and presumably also transformatory process. It may be that the markings and colourings that are to-day 
yet exhibited in the polytypical genera Polypoetes and Tithraustes represent the original appearance of the 
family the original types of which may besides have been of a rather small size; at least about 80 per cent, 
of all the species known have an average expanse of only 3 to 4 cm; but very few species ( Phaeochlaena 
Integra and Phanoptis cyanomelas) exceed this by attaining about 6 cm expanse. 
Most of the Dioptidae, particularly the species belonging to the genera Tithraustes, Polypoetes , Scotura, 
Dioptis, Euchontha, Stenoplastis etc., owing to their insignificant exterior, could not rivet any particular 
attention with the enormous legion of average collectors, the less so since they are generally met with at the 
habitats of the most beautiful and imposing lepidoptera of the globe. Most of the species were — not only 
by laymen —- valued as small Geometric! species, and only the more conspicuously variegated Myonia and 
Josia are found to have been taken more consideration of in older works, and even in the old trading catalogues 
there are mostly only forms mentioned which are allied to the latter. The fact that Proet, who wrote the 
catalogue mentioned below was the first monographer on this difficult and mimetically confused family evidently 
shows how much it was neglected. Besides, however, some Dioptidae are also in the habit of flying about 2 to 
3 m above the ground and of escaping up into the air on being pursued, as in Europe the Drepana cultraria, 
so that it may often be very tiresome to pursue them in disadvantageous districts’; and furthermore, those 
species flying in the daytime most exceptionally come to the lantern. In some, such as many Dioptis ( pallene , 
incerta , cyma , illerdina, egla etc.), the mimetic resemblance with the models from the families of the Danaidae, 
Syntomidae etc. swarming in large numbers at their habitats is so striking that even experts have great difficulty 
in discovering the imitators. Among the very numerous species wearing for instance the colours of Josia ena 
Bsd., and among which there are Erycinidae, Arctiidae, Syntomidae, Geometridae, and numerous microlepidcptera, 
we find but very few of the Josia themselves, and it is easily understood that only by intensely and carefully 
collecting them they may be brought in in numbers. The Josia here frequently play the same part among the 
Heterocera, as for instance the genus Napeogenes does among the Ehopalocera, where likewise the immense 
frequency of the models often diverts our attention from the imitator. 
Yellow bands on a jet-black ground is the predominant colouring of the mimetic genera; but since 
presumably all the Dioptidae are good flyers — partly even never resting and indefatigable flyers — their marking 
is not so subtile as we have noticed in many less intensely flying families, such as Erycinidae, Dlxomiinae, or 
Heliconiinae. Specimens of Monocreagra pheloides, for instance, captured at the same clearing of a forest, may 
differ from each other so much that the white subapical spot of the forewing may attain treble the size and 
quite a different shape from what it usually has; it may be snow-white or also light hyaline, band-shaped or 
oviform, coherent or divided; the hyaline areas may be distinctly bordered or also die away at their borders, 
and the size of specimens from the same district may vary so much that they may be much larger than the 
figure (70 d) or also half its size. The same variability is found in the Dioptis reslricta (69 1), and among a great 
many specimens of D. areolata all of which I collected at the same habitat and season near Santos there are 
not even two exhibiting the same size of their hyaline areas. 
The sexes of the Dioptidae, as a rule, do not exhibit any difference of the exterior, but in a number 
of species the <$<$ are distinguished by scent-organs which may sometimes most conspicuously alter the shape 
of the wings. For instance in the of Sagaris rejecta (71 i) the anal margins of the hindwing are doubled up 
into a fold in which there is a layer of hairs 1 to 2 mm long, which are whitish at the upper edge of the 
fold and black at the margin of the wing. In Sagaris dilatata-G (71k) there are on the sides of the 4tli 
to 6 th abdominal rings dense brushes of coal-black hair, and in the $ of Polyptychia fasciculosa (cf. the figure 
of ceron 71 k) we notice a still more complicated organ which even gave rise to the denomination of this strange 
species: on the thickened hind tibiae there are long white tufts of fine, slightly bent, silky hairs. The hind- 
margin of the hindwing exhibits a similar yellowish lock of coarser hairs, and besides the hindwing shows below 
the lower wall of the cell a deep skinny depression from the ground of which an extensible pencil sticks out. 
Under the microscope all these hairs prove to be circular fine bristles without sharp points or barbs, so that 
they are actually to be regarded as scent-organs and not protective organs. 
All these facts prove the Dioptidae not to be related to the preceding Arctiidae, but rather to belong 
to o n e group with the hereafter following families of the Drepanidae or also the Notcdontidae from which they 
show forth by the altering effects of mimicry in a similar way as the Ithomiinae from their relations of the 
Danais, Hestia, and Euploea. But before the family is definitely ranged, we have left it for practical reasons 
at the place where it is used to be looked for in the catalogues thus far existing, and we merely refer here to 
its presumptive position in the system. 
