Ageuonir^. INSECTS. Danaid.e. 257 
ascending the river Essequibo on the 10th of November; 
1838, saw one of these clouds, which continued cross- 
ing the course of the river for nine hours and a half. 
During this time the boat had ascended nine miles ; 
so that these butterflies formed a cloud nine miles in 
width, and of such length that it was nine hours and a 
half in crossing the river, notwithstanding the rapidity 
of the insects composing it; who could compute the 
millions of which it consisted ? 
Tlie Gonepteryx Rhamni^ or Brimstone butterfly, 
feeds in the larva state on the two species of Buckthorn 
found in this country, and also on other plants. 
The perfect insects, with their curiously-angled wings 
(from which they derive their generic name), appear 
in about a fortnight from the time that the larva has 
passed into the pupa state; they come out in summer, 
and continue on wing during the autumn months. They 
pass the winter in a state of lethargy, and reappear on 
the first mild sunny day of spring. Their flight is 
rapid and unsteady. 
The species of Colias are called Sulphur-yellow 
butterflies, from their prevailing colours. Two species 
are found in this country ; they are insects very irie- 
gular in their appearance. They are named Colias 
Edusa and Colias Hyale. In the arctic regions is 
found the Colias Boothii. Mr. Doubleday found that 
the species of butterfly mentioned by Mr. Darwin in 
his journal, is the Colias pyrrothea ; that naturalist, 
when H.M.S. Beagle was at sea and ten miles from the 
Bay of San Bias, saw vast numbers of butterflies of this 
species flying over the sea. Even with the aid of a 
telescope it was not possible to see a space free from 
them. The sailors of the Beagle cried out that it was 
snowing butterflies. 
Family— AGERONID^. 
Mr. Doubleday has formed with the genus Ageronia, 
consisting of butterflies from the New World, the family 
Ageronidcp. It is placed after the family Pieridte, but has 
little in common with it but its braced pupa. The fore 
legs are imperfect ; the palpi are three-jointed and con- 
vergent. There can be no doubt that this family should 
be placed in the Nymphalidce. Nothing is known of 
the larva. The. perfect insects have a short, rapid 
flight, and constantlj’’ alight on the trunks of trees. 
Most of the species are of a peculiar grey and white, 
very much resembling the colour of some barks and 
of lichens. All the species whose history is known, 
when they fly, produce a sound which, as Mr. Double- 
day was told by a good observer, resembled closely 
the rustling of a piece of parchment. 
Darwin, in the “Voyage of the Beagle,” thus refers to 
the habits of the Ageronia Feronia; — “ I was much sur- 
prised at the habits of the Papilio Feronia. This butterfly 
is not uncommon, and generally frequents the orange 
groves ; although a high flyer, yet it very frequently alights 
on the trunks of trees. On these occasions its head is 
invariably placed downwards, and its wings are expanded 
in a horizontal plane, instead of being folded vertically, 
as is commonly the case. This is the onlj’’ butterfly I 
have ever seen that uses it legs for running. Not being 
aware of this fact, the insect more than once, as I cau- 
VoT,. TI. 89 
tiously approached with my forceps, shuffled on one 
side just as the instrument was on the point of closing, 
and thus escaped. But a far more singular fact, is the 
power which the insect possesses of making a noise. 
Several times when a pair, probably male and female, 
were chasing each other in an irregular course, they 
passed within a few yards of me; and I distinctly heard 
a clicking noise similar to that produced by a toothed 
wheel passing under a spring catch. The noise was 
continued at short intervals, and could be distinguished 
at about twenty yards’ distance. I cannot form a con- 
jecture of how it was produced ; but I am certain there 
is no error in the observation.” 
Mr. Doubleday tried carefully to ascertain if there 
was any structure in the wing which seemed intended 
to produce it. He observed that they all presented one 
peculiarity ; it was this, that immediately above the 
nervure, quite at its origin, on the under side of the 
wing, there is a small round cavity, which is smooth 
inside and is covered with a very delicate membrane 
stretched across it, somewhat like the parchment of a 
kettle-drum, which, indeed, the cavity resembles in 
shape. In one species, Ageronia Aretlmsa, the swollen 
part of the costal nervule is divided by numerous trans- 
verse membranaceous diaphragms, which are placed 
obliquely, so as, when the nervure is rendered transpa- 
rent, to present the appearance of a screw with a very 
loose worm, which is inclosed in the nervure.* 
Family — DANAIDHU. 
The family Danaidm is distinguished from the next 
family, Heliconidae, by the species having shorter 
antennae, by the wings being for the most part shorter 
and more angular, and by the palpi, which scarcely rise 
above the forehead. 
The larvae are stout and cylindrical, smaller towards 
the head, and are furnished on one or more of the 
anterior segments with a pair of long, slender, flexible, 
fleshy tentacula, which are not retractile, and with a 
similar but often shorter pair on the segment before 
the last. The pupa is suspended, is short, smooth, 
somewhat ovate and contracted near the middle. 
The greater part of the species belong to the Old 
World; and they are found especially in the islands 
of the Indian archipelago. The species of the genus 
Euplcea are generally insects of considerable size, of a 
dark brown or black, spotted or streaked with white 
and light blue. 
The species of Danais are found both in the New 
and in the Old World. Danais Arcliippus is a species 
abundant even in the largest towns of the middle and 
northern states of America. Danais Berenice is fond 
of alighting on flowers, especially those of the Ascle- 
piadece. The Danais Eresimus is found often in 
hundreds together in the open plantations of Cayenne. 
The Australian variety of the Danais Limniaces was 
found by Captain King in countless myriads, when he 
was surveying the northern coast of Australia. It is 
said that the natives eat them. It is probable this is the 
very species of butterfly which Captain Cook saw in the 
* E. Doubleday — Genera of Diurnal Lepidoptera, p. 83. 
