AOEUONII)^. 



-INSECTS.- 



-Danaid.e. 



257 



aRoonding the river Essequibo on the 10th of Novemherj 

 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 those 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 ? 



The Goiiqiten/x Rhamni, or Brimstone butterfly, 

 feeds in the larva stale 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 

 jiassed into the pupa state; they come out in summer, 

 and continue on wing during the autumn months. They 

 jiass the winter in a state of lethargy, and reappear on 

 llie 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 irre- 

 gular in their appearance. They are named Colias 

 Edusa and Colias Hyale. In the arctic regions is 

 found the Colias BootMi. Mr. Doubleday found that 

 tlie species of butterfly mentioned by Mr. Darwin in 

 his journal, is the Colias pyrrothm ; that naturalist, 

 when IT. 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 

 Ageronidai. It is placed after the family Pieridfe, 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 NymphalidcB. Nothing is known of 

 ' the larva. The perfect insects have a short, rapid 

 flight, and constantly 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 fl}', 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 Fcronia: — " I was much sur- 

 prised at the habits of the PapilioFeronia. This butterfly 

 is not uncommon, and generally frequents the orange 

 groves; although ahigh 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 only butteifly I 

 have ever seen that uses it legs for running. Not being 

 aware of this fact, the insect more than once, as I cau- 

 VOL. 11. 



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 ara 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, wdiich 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 Arethusa, the swollen 

 part of the costal nervnle 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— DANAIDiE. 



The family Danaidai is distinguished from the next 

 family, Heliconida;, 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 larvaj 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 tlie 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 

 Eiqjlcea 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 A rchippus 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- 

 piadem. The Danais Eresimus is found often in 

 liundreds together in the open plarjtations of Cayenne. 

 The Australian variety of the Danais Limniaces was 

 found by Captain King in countless myriads, wlien 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. 



2K 



