THE PRACTICAL ENTOMOLOGIST. 



43 



Colors, black and 

 yellow. 



jacket" with black and yellow. The upper figure 

 in the annexed cut shows one of these last — the 

 Si/rphiis politus of Say — the hair-line exhibit- 

 ing its natural length. The 

 lower figure shows the larva 

 of a species of Syrphus trans- 

 fixing an Aphis with its point- 

 ed mouth, and sucking out 

 \its juices as it holds it help- 

 lessly suspended in the air. 

 Unlike the two groups of lar- 

 vte, which we have just been 

 considering, these Si/rphua 

 larvae are slow-going, fleshy, 

 footless, whitish maggots, and the 

 egg from which they take their ori- 

 gin is always deposited by the pa- 

 ' rent-fly right in the midst of a colo- 

 Color, whitish, ny of the Plant-lice, whereas the 

 eggs of the others are sometimes laid 

 a considerable distance ofi". The reason is obvious. 

 The former are active six-legged insects, and hav- 

 ing good eyes of their own can readily seek out 

 their prey. The latter are sluggish legless fellows, 

 and, strange to say, they are perfectly blind. 



Few things are more amusing than to watch the 

 proceedings of one of these Syrphus larvae among 

 a lot of Plant-lice ; which may be readily done 

 even with the naked eye, though a pocket-lens is a 

 great assistance. You see a leech-like maggot slow- 

 ly crawling along, and swaying his pointed head 

 first to one side and then to the other, as an ele- 

 phant moves his trunk. The head comes within a 

 hair's breadth of a plant-louse, and you fancy that 

 the poor plant-louse is doomed. No such thing ; 

 the S^rphus has not actually touched his prey, and 

 like a blind Cyclops he goes groping along till acci- 

 dentally he touches one. Then, like a flash of 

 lightning, he impales his victim, hoists him in the 

 air, in spite of all his kickings and strugglings, and 

 in a few seconds has sucked him as dry as a bone, 

 exhibiting, under the lens, as much greedy gusto, 

 as an Alderman would do in swallowing a plate of 

 turtle-soup. Jerking away the empty skin, he 

 then proceeds with grave and earnest solemnity, as 

 if he were well aware that he is performing a sa- 

 cred duty towards society, to search out another 

 and another victim ; till having satisfied both his 

 appetite and his conscience, he reposes for awhile 

 from his labors, with the pleasing conviction, that 

 he has tickled his own palate, and at the very same 

 time discharged his obligations towards that sublu- 

 nary world, of which he forms so important a mem- 

 ber. 



It is almost impossible to find a group of plant- 

 lice of any magnitude, without one or more of these 

 Si/rphus larvas among them ; and yet Farmers and 

 Gardeners and Orchardists, with hundreds of such 

 scenes as the above constantlv under their very 

 noses, go through life with their eyes shut and fail 

 to see them. As the old proverb has it, " None 

 are so blind as those that won't see." It may be 

 added here, that most of the Syrphus flies are dis- 

 tinguishable, by the habit that they have of occa- 



sionally hovering motionless for a few seconds in 

 the air, like our Sparrow-hawk. In both cases the 

 object probably is to discover the more readily that 

 prey, which a wise Providence has appointed them 

 to attack; the Sparrow-hawk carrying ofi' its quarry 

 to its nest, and the Sj/iphus fly building no nest at 

 all, but laying its egg where it instinctively knows 

 that its future fomily will find abundance of food. 



Besides the above three principal groups of ene- 

 mies. Plant-lice, in common with most other groups 

 of Insects, are attacked by Ichneumon flies, which 

 inject a single egg into their bodies with their ovi- 

 positor. As in similar cases, this egg becomes a 

 larva, and gradually devours the body of the living 

 victim which it inhabits, finally emerging as a mi- 

 nute four-winged Fly, belonging to the sub-group 

 Aphidhts of the group Bracon of the great Ichneu- 

 mon family. In a small parcel of Plant-lice sent 

 me from Kentucky, I counted no less than two or 

 three dozen of these minute Ichnevmon flies, which 

 had hatched out on the journey. (See Practical 

 Entomologist, Vol. I, p. 100.) Plant-lice at- 

 tacked in this manner, like other ichneumonized 

 insects, afiix themselves firmly to the surface on 

 which they stand, and may be otherwise distin- 

 guished from such as are in good robust health, by 

 their swollen and bloated bodies. If they are care- 

 fully opened, the maggot-like larva of the Ichneu- 

 mon fly may often be found coiled up inside them. 



Besides all the above, there are many other in- 

 sects which occasionally or habitually prey upon 

 plant-lice. I have noticed a "Devil's darning-nee- 

 dle" (^Agrion) flying among my currant-bushes 

 with one of the Currant-bush Plant-lice in its 

 mouth. Certain wood-wasps also, (^C'rabro family,) 

 provision their nests with the bodies of these in- 

 sects, in Europe and probably in this country as 

 well ; for in the heart of one of the Pine-cone like 

 galls, which are so common everywhere on the tips 

 of the twigs of a Willow, (Salix cordata,) and which 

 have been named strohiloidcs by Baron Osten Sack- 

 en, I once found a little heap of plant-lice, which 

 had evidently been placed there as provision for 

 the young larva of some kind of Wasp or other. 

 A species of the true bugs (Heteroptera) known as 

 Nabis fera — an elongate, long-legged, grayish- 

 brown insect, about J inch long, belonging to the 

 Reduvius family — is likewise said by Dr. Fitch to 

 attack the Grain Plant-louse ; but this Bug, as I 

 have noticed, is confined to low-growing plants, and 

 its place upon trees and shrubs seems to be sup- 

 plied by other members of the same family, the 

 Reduvius raptatorius of Say and the R. multispi- 

 nosus of DeGeer. Finally, the all-devouring spi- 

 ders, which are spread everywhere, and which all 

 of them feed exclusively upon animal food, must, in 

 all probability, occasionally make a meal oflF the 

 plant-lice. 



As a general rule, I do not believe that plant- 

 lice are injurious to fruit-trees, because in limited 

 numbers they operate as a summer-pruning, and 

 tend to throw the tree to fruit; and their numer- 

 ous enemies usually prevent them from increasing 

 to any alarming extent for any great length of time. 



