HARD WICKE'S S CIENCE- G OSSIF. 



223 



nest, and k good substitute for this is a well-picked 

 chicken-bone, given very occasionally, but it must be 

 borne in mind that "meat" raw or cooked will 

 cause the bird to pluck out its feathers, A bird fed 

 as recommended by the authorities whose names 

 I have mentioned will live for a great number of 

 years without asthma or any other complaint ; and 

 there is no doubt that a pair of them would breed, if 

 provided with a suitable nesting-place in the shape of 

 a hollow-tree, or even a barrel partially filled with 

 sawdust, jDlaced in an empty room or a strong iron 

 aviary of convenient size. 



An acclimatised grey parrot is very hardy, but like 

 all other birds is very impatient of draughts. Vast 

 numbers of these birds soon after being landed in 

 this country die of consumption, induced by over- 

 crowding during the voyage, and dirty drinking- 

 water. As a rule parrots are very fond of bathing, 

 though some individuals cannot be induced to wash 

 themselves in a cage, and as a consequence become 

 scurfy and rough as to their plumage ; these should 

 be gently sprinkled with tepid water from a garden 

 syringe, or the rose of a water-pot, once or twice a 

 week in the summer, and then placed out in the sun 

 to dry themselves. 



W. T. Greene, M.D. 



Moira, Pcckham Rye. 



INSECT SWARMS. 



THE abnormal profusion some years of certain 

 kinds of insect life, their sudden appearance, 

 and equally sudden disappearance, must often have 

 created much astonishment. The causes operating 

 in this development are by no means easy to account 

 for ; still the fact remains, and is so patent as to 

 attract, not that alone of the entomologist, but 

 general attention. 



At one time plants and trees are infested with 

 swarms of Aphides ; the beans in our gardens are 

 black with Aphis rumicis ; the flowers in our con- 

 servatories are covered with what is popularly known 

 as the " green-fly," and the hedges drip with the 

 frothy distillations ol Aphrophora spmnaria. Another 

 year we have to lament the injury by the larvae of 

 the .saw-fly {N'ematits ribesii) to the gooseberry and 

 currant bushes, which are stripped by them almost 

 bare of leaves (to plants both as stomach and 

 lungs) so that the fruit never comes to perfection. 

 The usual habit of the larvK is to attack the lower 

 branches first, and work upwards till the whole bush 

 is defoliated, and presents a curiously grotesque 

 appearance of interlacing thorns. 



Sometimes the air, in spring and summer, teems 

 with the two species of cockchafer {Melolontha 

 vulgaris and Rhisotrogus solstitialis), which buzz in 

 our faces, and apparently delight in annoying our- 



selves, horses, cows, and other animals, with their 

 persistent assaults. 



A.D, 1877 will long be remembered as the Colias 

 Ediisa year ; this uncertain butterfly then appeared 

 in the utmost profusion throughout the length and 

 breadth of the land, being more common even than 

 the garden whites {Picrisbrassic(e,P. rapcv, and/', napi) 

 since which we have had only a few stragglers here 

 and there ; and it is now a long while ago that its 

 congener, C. hyale, has favoured us with a visit. 



In the same year the apple trees suffered con- 

 siderably from the large numbers of the gregarious 

 larvcc oi Bombyx ncitstria. In the earlier stage when 

 the young caterpillars feed together under a web, it 

 is not very difficult to get rid of those within reach, 

 and a neighbour of ours adopted the ingenious 

 device of firing with powder only into the trees, and 

 so blowing off" those higher up ; afterwards when more 

 grown they disperse, and are more troublesome to 

 remove. 



In the year following, the larvae of \ 'ancssa poly- 

 chloros swarmed on the elms {Ulmus campestris) 

 surrounding our house ; curiously enough, neither 

 caterpillars nor imagines have since been noticed. 



The altogether unprecedented abundance of Pliisia 

 Gamma in 1879 will not soon be forgotten. I saw 

 whole fields of peas which the larvae had left almost 

 without a leaf; the larvae themselves could have 

 been collected in thousands. This season there are 

 comparatively speaking no gammas ; their place 

 however has been supplied, though more locally, by 

 immense swarms of C/tarceas graminis, which in the 

 larval state, are reported in Lancashire to have 

 played sad havoc with vegetation. The moth does 

 not occur to my knowledge in this district ; but 

 Tryphcvna pronuba has done its best to rival it and 

 the gammas of 1879. They were to be seen 

 hovering over every flower, and proved a complete 

 pest at sugar. 



The present season too has produced swarms of 

 insects of another order. In the spring the pendulous 

 racemes of the sycamore {Acer pseudo-plataniis) were 

 well-nigh hidden with a black dipteron {Dilophus 

 febrilis), looking as if dipped in ink. They were 

 eventually dispersed by the high winds which 

 prevailed towards the close of May. 



Now we may fairly suppose that all these vast 

 numbers of insects must have deposited a corre- 

 sponding quantity of eggs. What of these : did the 

 greater part perish, or are they only waiting favourable 

 conditions to bring them forth in swarms again ? 



Some species of Lepidoptera, such as P. car did, 

 C. Ediisa, and C. hyak seem to come out at some- 

 thing like regular intervals. Two hypotheses appear 

 reasonable to me for accounting for this, and the 

 exceptional development at times of other insects. 

 In the one case we will imagine that the insects are 

 born in this country ; in the other, that they are 

 immigrants from some foreign lands. This idea 



