ERI 



pupae. Those which are intended to rest until another 

 season do not swell until that season approaches. 

 This swelling cannot be produced by heat, because 

 all the pupae, those which do not as well as those 

 which do swell, are kept in an equal tempera- 

 ture, and experience the very same treatment. Per- 

 haps," he adds, " they are endowed above by some 

 differing principles which require the differing periods 

 of one, two, and three seasons to repair and bring them 

 to complete maturity, and render them capable of 

 accomplishing the full intentions of their beneficent 

 Creator." Without offering any opinion upon the 

 cause of the prolongation of the chrysalis state, we 

 may satisfactorily account for the swelling of the 

 chrysalides, without attributing it to the acquisition of 

 fresh matter, the swelling of the substance already 

 there.or to the action of heat, by considering, that imme- 

 diately before assuming the perfect state an increased 

 quantity of air is imbibed by the insect, for the pur- 

 pose of distending the exceedingly numerous ramifi- 

 cations of the newly developed respiratory organs. 

 " This insect," further observes Mr. Haworth, " is 

 probably of great service to many of our soft- 

 billed birds, at a season when little and insufficient 

 quantities of food are to be procured, especially in 

 severe and rigorous winters, in which the ground 

 remains a long time covered with snow, when this 

 poor moth and some other species of lepidoptera (as 

 soon as escaped from the pupa) stick torpid upon the 

 trunks of trees, where these birds readily find and 

 devour thorn*, and thus e>c;tpe from hunger at a 

 time when worms or other terrestrial food are either 

 difficult or impossible for them to procure ; these 

 birds, thus saved, are of incalculable service the fol- 

 lowing spring, in restraining within due limits the 

 insect despoiiers of the vegetable kingdom ; during 

 which they never fail to cheer us with their charm- 

 ing songs, and lessen the destructive numbers of 

 caterpillars in our orchards and gardens, until in 

 their turn they become the prey, the necessary prey, 

 of some insidious weasel, or birds more powerful 

 and rapacious than themselves ; I repeat necessary 

 prey, because they themselves would become too 

 numerous if never destroyed, to the total extirpation 

 of various insects, whose existence in the scale of 

 things is as essential as their own to keep within 

 appropriate bounds certain vegetables which other- 

 wise would multiply to the total exclusion of other 

 weaker and smaller, but equally necessary species ; 

 and so on, ad uifinitnm, until, at length, the head, and 

 prince, and king, of all created beings, man himself, 

 would feel the chusm, and experience inevitable woe." 



ERIOL^ENA(l)ecandolle). An ornamental ever- 

 green shrub, native of the East Indies, belonging to 

 Syttneriacece. It is readily propagated by cuttings 

 struck in peat. 



E RIO P HO RUM (Linnaeus) is a genus of grass- 

 like plants, belonging to the order Ci/pcrace<e, and is 

 the cotton giass common on moors and bogs in many 

 parts of Britain. 



ERIOSPERMUM (Jacquin). A genus of bulb- 

 ous rooted plants indigenous in Southern Africa. 

 The flowers are hexandrious, and belong to the natu- 

 ral order Asphodelcee. Generic character : corolla 

 six-petaled, spreading; stamens inserted into the base 



All insects, except lepidoptera in the winged state, conceal 

 themselves during the time of severe frosts in places inacessible 

 to birds. 



E R D I U M. 443 



of the petals ; filaments flatted and eonnivent ; anthers 

 double arrow-shaped ; style triangular ; stigma three 

 lobed ; capsule three-sided, three-celled, cells with 

 several seeds. These bulbs are grown in loamy turf, 

 moor earth, and sand mixed, and are increased by 

 off-sets. 



ERIOSTEMON(Smith). A genus of ornamental 

 evergreen shrubs introduced from New Holland. 

 The flowers are decandrious, and the plants are asso- 

 ciated with the natural order Rosaccce. They have 

 some resemblance to Diosma or Adcnandra, and are 

 equally easy of culture in the greenhouse. 



ERISTALIS (Meigen), a genus of dipterous in- 

 sects, belonging to the section Athericera, and family 

 Si/rp/iidee, having the thread of the antenna; pilose, and 

 the external cell at the tip of the wing (situated near 

 the angle at the extremity), with a deeply rounded 

 notch at its outer side. The body is thick, the eyes 

 pilose, the hind legs simple, and the third joint of the 

 antennae large and patelliform. The early states of 

 these insects have been long known ; they are de- 

 scribed by Swammerdam and Reaumur. The larvas 

 are in the number of those which reside in the mud 

 of stagnant water, and which have been termed rat- 

 tailed larva 3 , from the extraordinary elongation of the 

 terminal segment of the abdomen, which is furnished 

 at its extremity with an organ of respiration, which is 

 easily brought into contact with the air at the surface, 

 and at the same time permitting the larva?, by the 

 various degrees of extension of which it is capable, to 

 retain its situation in various depths. Before passing 

 to the pupa state the insect leaves the water, buries 

 itself in the soft margin of the sides, the respiratory 

 tube ceases its functions, the body contracts, the skin 

 hardens, and becomes at length the covering of an 

 inclosed pupa, in which the organs of respiration 

 appear in the form of four small horns, placed at the 

 fnfcnt part of the body. The perfect insects delight 

 in flowers, of which they suck the nectar, in bruised 

 fruit, and in the sap which exudes from wounded trees 

 of which they are not less fond. The females often 

 deposit their eggs without ceasing their flight for this 

 purpose ; they suddenly drop themselves to the sur- 

 face of the water, leaving an egg there, and as sud- 

 denly rise again. In this respect they agree with the 

 dragon-flies. When settled upon leaves or other sur- 

 faces, the abdomen is alternately elevated and de- 

 pressed from time to time. Their flight is very strong, 

 and their movements, when on the wing, often very 

 sudden : often they may be observed suspended as it 

 were in the air, balancing themselves on their wings, 

 which are kept in so rapid a motion as to be scarcely 

 perceptible, darting off at the least approach of danger. 

 In most of the species there are many generations in 

 the course of the year. They are to be found in the 

 winged state from the commencement of spring until 

 the arrival of winter. There are about twenty British 

 species of this genus, including the Muscn intricaria, 

 nemorum and Arbustorum of Linnaeus. The Musca 

 tenax of Linnaeus, and some other species, form a dis- 

 tinct section in the genus, having the bristle of the 

 antenna? naked. 



ER1THALIS (Linnaeus). A genus of two species 

 of trees, one is a fruit tree in Jamaica, the other 

 deciduous ornamental of India. They are pentan- 

 driotis, and belong to the order Ruliacece. 



ERODIUM (Heretier). A genus of annual and 

 perennial herbs, formerly classed with the geraniums. 

 Linaaan class and order Monadefphia Pentandna, and 



