34 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



having a blackish spot or mark on the lower side of the upper pair. The 

 larvaB, pupte, and perfect insects appear to prefer the side of a branch 

 just above a bud or in the axils ofthe leaf-stalk, and the head ia 

 generally hidden under the bud. These insects appear to be 

 gregarious, and fond of herding together in groups of twelve 

 or more. They elaborate and void a sweet clammy substance 

 like honey-dew, derived from the sap of the tree, which, fall- 

 ing on the leaves and limbs below, gather all the dust and dirt, 

 causing the tree to have a very lilthy appearance. This so- 

 called honey-dew is generally found on the upper surface of 

 the leaves and branches, and evidently comes from insects 

 feeding directly over or above the clammy places. As it is 

 voided it falls on the leaves below, and is eagerly sought after 

 by ants, which, when a tree is much infested by Fsylla pyri, 

 may be seen in swarms running up and down the trunk. 

 The same remedies may be recommended for these insects as are men- 

 tioned for plant-lice and leaf- hoppers. They are also probably destroyed 

 by chickadees and golden-crested wrens, as we have seen these little 

 birds hanging head downward on a particularly-infested tree in Novem- 

 ber and even in dead of winter, busily employed in searching every hole 

 and corner for hidden insects. The figure is magnified. 



The Aphides, or plant-lice, are exceedingly injurious to horticulture, 

 inserting their long beaks into the tender shoots and leaves of plants 

 and then sucking out their sap. These insects are generally of very 

 small size, having antennae of 5 to 7 joints and a long three-jointed 

 beak, or proboscis, for puncturing plants, and then sucking out the sap. 

 Their bodies are soft, rounded or flask-shaped, and apparently only con- 

 sist of a skin filled with a liquid ; their legs are long and very slender, 

 and many of them have two upright processes or tubercles on the hinder 

 part of the abdomen, from which a sweet gummy substance is occa- 

 sionally ejected, which is eagerly sought for by ants and other small 

 insects. The wings are generally transparent, and the upper pair are 

 much larger than the lower, and are furnished with strong nerves or 

 veins, which pass outward from the costal or outer marginal vein ; these 

 wings are very much deflexed at the side of the body when the insect is 

 at rest. Dr. Burnet states that in early autumn the colonies of plant- 

 lice are composed of both males and females ; the female after pair- 

 ing deposits her eggs and dies. Iilarly in the spring the eggs are 

 hatched, and the young plant-lice puncture the plant, suck the sap, and 

 increase in size, the whole brood consisting of individuals capable of 

 reproducing their species without any connection with a male by a 

 species of gemmation or budding forth. These summer broods are 

 wingless. The second generation and several others pursue the same 

 course, being sexless, or at least without the trace of a male among 

 them, and so on indefinitely until the autumn, when winged individuals 

 are produced, which lay eggs for the spring brood of sexual individuals. 

 Bonnet obtained nine generations and Duval seven by this process of 

 gemmation in one season, and Packard states that Aphis dianthi, the 

 plant-louse of the pink, continued to propagate by gemmation without 

 any males for four years, in a constantly-heated room. It has been 

 supposed that the final autumnal set of plant-lice were males and 

 females alone, but Dr. Burnet states that on examining the internal 

 organs of the winged individuals many of them were not females 

 proper, but simply the ordinary gemmiferous or summer form. As 

 there are peculiar plant-lice infesting different plants, the number of 

 species must necessarily be very great. 



