44(5 



JOUKNAii OF HOBTICOLTUEE AND COTTAGE 6ARDENEB. 



[ stay 80, 1873. 



a question of some interest— namely, as to the deuompasitiou 

 which the juices of plants unclorgo iu the digestive appiiratus 

 of the aphis tribes. It is a papular supposition, I thLnli, that 

 these creatures are something lilse certain pigs whose history 

 the poet Pope has seen fit to immortalise, or the reverse of 

 that. In not very elegant phrase he aUudes to these in one 

 of his satii-es as excreting the food they had just swallowed at 

 the trough in a condition exactly resembling that iu which 

 they received it. So it is supposed that aphides give forth the 

 sap they have pumped up iu almost a pure state; but this 

 can hardly h2. A comparison of the sap of plants and the 

 excretions of the aphides found thereupon would most pro- 

 bably show that a chemical change was worked, and the honey- 

 dew was not unaltered sap nor an atmospheric product, as has 

 been fancied — at least not generally, thougli there may be 

 honeydew which is not deposited by aphides. The attractive 

 influence which the fluid ejected by the latter exercises upon 

 ants proves, were proof necessary without chemical testing, 

 that it is largely saccharine. 



We commenced by remarking that we were about to discourse 

 upon aphis life, but in reality it will turn out that aphis death 

 is rather the topic ; for it is necessary, by way of wholesome 

 consolation for the afflicted gardener, greatly vexed in spirit 

 through these tiresome though petty pests, to show that, be- 

 sides birds and other enemies of a larger sort, there are many 

 insect-destroyers of aphides. Some of these are very notice 

 able, others carry on their work in an insidious way. Aphides 

 are decidedly peculiar in their utter disregard of the dangers 

 which environ them from then- first start iu life until they 

 reach such a degree of maturity as they attain, which is, as 

 already observed, far from being full aphishood iu many gene- 

 rations. Some insects there are which, when attacked by other 

 insects, make a bold fight of it, or at least use their endeavours 

 to escape, but not so these soft-bodied creatures ; they receive 

 the assaults of their foes with a pusillanimity which, if they 

 were higher iu the scale of creation, would awaken pity or 

 contempt. 



Ladybirds as they are popularly called — the weU-kuowu 

 little beetles belonging to the Coccinella genus, are generally 

 spoken of as holding a conspicuous place amongst the insect- 

 destroyers of aphides. No doubt 

 they do devour many, both while 

 they are themselves in the laiTal 

 state and also when they are 

 imagos, and the principal workers 

 are the species bipunctata and sep- 

 tempunotata. It has been several 

 times recorded that these species 

 have been observed to foUow the 

 aphides in their short migrations 

 from one spot to another. But with 

 the best intentions in the world, 

 for which one is wilUng to give 

 them credit, ladybirds are often 

 caught napping when they ought to 

 be slaughtering aphides or laying those eggs which should 

 produce the more rapacious larvic. One reason of this is 

 that these beetles are sensitive to cold, and at certain times 

 in the spring, just as aphis life is getting proUfic, ladybirds 

 will be found creeping about in a half-torpid state, or skulk- 

 ing under the leaves which have been contorted by the 

 aphides, and lazily devoiuing a few of these. As far as I have 

 observed, the eggs of Coccinella; are deposited in the spring 

 by those insects which have hybernated, and they hatch out 

 more tardily than those of the aphides. Some enter])rising 

 individuals have suggested that plans should be set on foot for 

 the rearing of these beetles on a large scale, and their subse- 

 quent distribution in the particular places where they would 

 be of most utility. But other insects, such as the Syrphi, 

 which could hardly be thus nurtured, are much more effective 

 foes of the aphides ; and under any circumstances human 

 efforts would be better expended in making direct onslaughts 

 upon the aphis hosts than in multiplying their insect enemies. 

 The latter, of course, should not be killed or disturbed. 



Many persons in their stroUs through the woods find them- 

 selves greatly annoyed by the pertinacious attacks of flies be- 

 longing to the Syrphina family. The larvsc of some of these 

 feed upon aphides, and they are furnished natui-ally with a 

 weapon which enables them to do great execution with httle 

 trouble to themselves. This instrument is a kind of thr-ee- 



forked trident, conceniing the use of which a writer says 



" These larvm may often be seen laid at ease on a leaf or twi" 



Coccinella septempunctata. 



envii'oned by hosts of aphides, and these, so far from escaping, 

 actually walk over the back of theii' enemy. When disposed 

 to feed he fixes himself by his tail, and being bUud gropes 

 about on every side as the Cyclops did after Ulysses and his 

 companions, till he touches an aphis, which he immediately 

 transfixes with his trident, elevates into the air that he may 

 not be disturbed by its struggles, and then devours. 



Tliere are a good many insects which are far from agreeable 

 in the odours they emit, but of all villainous stenches that given 

 off by the Lace-winged fly (Chrysopa or Hemerobius Perla), and 

 which adheres persistently to the fingers is the worst. " What 

 a beautiful fly ! " is the exclamation of the observer, who in 

 beholding one of them resting upon a leaf admires the delicate 

 structure of the wings, theii- lustrous tint, and the bright 

 golden eyes ; and this sentimental feeling which is thus called 

 forth, is speedily changed into disgust, except in the case of a 

 naturahst, perhaps, when the insect is grasped. It rarely flies, 

 however, until the dusk of evening, though noticeable on plants 

 or trees during the day, and as it is rather conspicuous, the 

 peculiar odour with which it is endowed may have been given 

 it for its protection. The eggs are curiously arranged on the 

 lea%'es of various plants. They may be found iu groups of a 

 dozen or twenty, each supported on a slender footstalk, the 

 eggs themselves being pearly and circular. The microscopists 

 have occasionally thought these were fungi, but if they be kept 

 in a box for a short time the young larvie ma.y be caught iu 

 the act of cautiously descending from their elevated position to 

 the leaf below-. The writer, however, and no one else so far as 

 he is aware, has been able to catch the female in the act of 

 oviposition. The larva of the Lace-winged fly has a pair of 

 mandibles (or shall we call them nippers?) wliich are long, 

 curved, and pointed. If we are to believe one author, a larva 

 of this species can seize and kill an aphis in half a minute ; 

 and as their voracity is remarkable, and therefore then digestive 

 powers proportionable, they can considerably reduce iu numbers 

 a colony of aphides into which they have been obtruded. 

 Should a supply of aphis flesh fail, the larvie of Perla fall to 

 upon any small fry of the caterpillar sort wliich may be handy, 

 nor do they hesitate sometimes to play the cannibal. Having 

 attained to adolescence, each larva encloses itself in a sUkeu 

 investiture, and lies torpid as pupa through the winter. This 

 larva has been called the aphis Uon ; it has not the unpleasant 

 odour which is the concomitant of the imago state. 



On very good authority it is asserted that ants devour 

 aphides occasionally, nor is there anything astonishing in the 

 fact, though the aphides serve also as the " milch cows " of the 

 more active insects. We ourselves eat cows, as well as milk 

 them, at least sometimes — not by preference, since we find ox- 

 meat better. A writer in " Science Gossip," is, however, 

 evidently wrong in thinking that the diied and empty skins 

 of aphides to be seen on plants are necessaiily signs that they 

 have been devoured by ants or by other enemies. Nor does it 

 seem likely that the formic acid ants emit is hurtful to plants, 

 as he suggests. StiU he may be right in his statement that ants 

 take too much honeydew at times, and then roll helplessly 

 about on the stem, quite " drunk and incapable," for Dr. Gray 

 writes — " I know that ants do get dnmk. They will pass up 

 the stem of Prunus Laurocerasus, and think the secretion 

 from the gland on the petiole, until they get so queer that they 

 cannot find their way down again." For their own benefit, 

 and from no kindness to the aiihides, ants have been observed 

 to guard a colony of apliides from the predatory visits of the 

 tenants of other ant hUls. They also nurture them in their 

 hills during the colder months, and Kii'by has given an in- 

 teresting account of the proceedings of the common yellow ant, 

 which he calls the gi-eatest cow-keeper of the family. He found 

 that dm'ing the spring the eggs of aphides (chiefly those of 

 A. radicum), are watched over with great care by the ants, and 

 placed in the sun at suitable times. But for aU tliat, there is 

 stUl probability that some species of ants occasionally devour 

 aphides, which may be a sUght set-off against the injuries we 

 have to charge ants with committing in our gardens. 



Various two and four-winged flies of the Hymeuopterous 

 and Dipterous orders make aphides their special food. One of 

 these is distinguished from its coadjutors by the cautious way 

 in which the larva goes to work upon its aphis victims. Only 

 a single egg is deposited by the parent fly on each aphis, and 

 when this hatches out, the larva feeds very coinfortiibly in the 

 body, which swells and turns brown as the aphis dies. But 

 this dies, unfortunately, before the feast of its parasite has 

 come to its conclusion ; so its tormentor, to prevent the carcase 

 being wafted away by the wind, cuts a hole through the integu- 



