Pull. 1. VIII. 1915. 
GERYDUS. By H. Fruhstorfer. 
817 
entirely corresponding to G. boisduvali. The forewings differ from the latter species by the absence of a white 
subanalzone which, however, is still faintly indicated. $ differing from the 8 by perceptibly dentate hindwings. 
North East Sumatra, particularly on the Battak Mountains. 
b) Group of species Gerydus Bsd. 
a) Forewing with a thickened base of the anterior median and a more or less broad androconial spot. 
G. boisduvali, an insignificant, most variable species. It is the most widely distributed among all 
the Gerydinae, but xrevertheless the material being at our disposal still remains entirely insufficient. Occurring 
from Sikkim to New Guinea, it is common in single islands, in Sumatra, however, so rare that only one couple 
is for certain known from there. The species bears itself very unstable to geographical influences, and on the 
continent it seems besides to be subject to metagenesis. The most interesting fact may be the intermitting 
of forms with quite a narrow sexual spot of the forewing (Hongkong, South Borneo, Lombok) beside races 
with broad, disc-like androconial accumulations (North Borneo, Java), unless two species having hitherto 
not yet been recognized are concealed among these sexually modified forms. Then there also occur colorial 
anomalies by 88 exhibiting a whitish subanal region on the under surface of the forewings, and by 88 ■— though 
rarely — being without this light area. The $ differs from the 8, without counting the usual dentate hindwings, 
by a series of whitish or yellowish, differently large spots which are generally more expanded beneath or often 
covered with blackish or grey. The sexual organs are, compared with those of the closely allied G. biggsi Dist. 
(141 g), distinguished by broader and shorter uncus-sheets. The valve is likewise shorter. - — milvius Fruhst. milvius. 
(141 f, misprinted into milvina). Based upon the dry period form mentioned by Swinhoe (Lep. Ind. Vol. VII, 
p. 189) and figured on t. 613 fig. 1 c-—e. Forewings of the $$ with a band reminding us of croton , though it 
is mobe obliquely placed, being peripherically delicately powdered with a brownish grey. Shape generally 
smaller and the under surface lighter than in boisduvali from Java. Type from Sikkim; from Burma there 
are similar specimens reported and I myself found a very similar form in South Annam in January and February. 
— assamensis Doh. based upon 88 with a large whitish spot at the apex of the cell of the forewing and pro- assamensis. 
minent bands on the under surface of the hindwings. Very rare, only few specimens known. — irroratus Druce. irroratus. 
Siam. A remarkably large form collected by Mr. Godfrey on the Petchaburi River to the south of Bangkok. — 
chinensis Fldr. Hongkong. Habitus very large, as a rule with two intramedian yellowish diffuse spots before chinensis. 
the anal angle of the upper surface of the forewing. The egg, according to a figure by Kershaw (Butt. Hongkong, 
t. 6 a fig. 19, 1907), is quite flat with four edges and as many grooves, and looks like a folded Japanese paper 
lantern. Larva discovered by Kershaw, when creeping out almost cylindrical, assuming a limacidae-like shape 
only later on. Colour at first light yellow with a distinct purple dorsal line and some fine hairs on its brown 
head and at the last segment. In the last stage the larva turns greenish yellow with purple-brown stripes, the 
second segment swells up, so that the head may easily be hidden under it, which is nearly always the case when 
the larva is at rest. The larva feeds on aphis, some bites being sufficient to devour them. After their meal, 
the larvae lipk off their feet, exactly like the mantis use to do, too. The aphis on being devoured are pressed 
against the plant or held suspended into the air, sometimes even carefully picked out and apparently examined 
by smelling whether they are edible. The aphis themselves are not aware of the danger threatening them by 
the Gerydus-l&i-v&Q, for sometimes they climb across the larvae or they crawl round them. The eggs of the 
butterfly are deposited in the midst of a heap of aphis and clued on with their entirely flat base, so that they 
cannot glide off nor be removed by the aphis. Before the larvae change into a pupa, they lose their scanty 
hair and begin for some time to cast off their snail-like laziness and wander restlessly about. On having found 
a suitable place, they spin some threads near the head and tail; sometimes they also make themselves a belt. 
The apex of the abdomen is flattened, forming a disk and thus a good point of support. At each side of the 
seventh segment there is a small projection. The pupal stage in the rainy period lasts for about 10 days, the 
larval stage in the same period about 15 days. The imago, in Hongkong, passes through its complete 
development during every month of the year, except the cold months of January and February. The imago 
itself has green eyes and prefers shady and wet places below large trees with neglected brushwood. Although 
it is on the move all day long, still it occurs the most frequently towards evening. The $ deposits its eggs towards 
evening shortly before dawn sets in entirely on twigs and leaves being occupied by aphis, and across which 
two species of ants run, Polyrachis dives 8m. and Dolichoderus bituberculatus Mayr. Both the aphis and ants 
feed from the sap of the plant, whereas the ants besides make use of the aphis as milch-cows. Before the $ 
deposits its eggs, it undecidedly flies up and down, wandering about here and there in the leaves, till at last 
it makes two or three attempts to deposit a single egg in the midst of the ants and aphis. It then rises and for 
some time drinks from the sap of the plant of which the 88 and ?? are very fond, so that sometimes 5 or 6 
are seen sitting together. The ants neither care for the butterflies nor the eggs, nor the larvae of the Gerydinae. 
IX 
103 
