A HISTORY OF ESSEX lie dormant through the winter and produce the generations of the suc- ceeding year. Some of the Essex gardeners seem to labour under strange delusions about Aphides, for they will tell you that like divers other noxious insects they come over with the east wind in the spring, and that they are especially abundant ' after we have had a heavy fall of honey-dew.' They do not seem to know that the sweet clammy sub- stance called honeydew is a secretion from the Aphides themselves, and that it is because they are already abundant that the ' fall ' is heavy. The species that infest the beech, birch, cabbage, currant, dock, elm, honey- suckle, lime and rose are too well known examples of the tribe, but to name all its food plants we should require a second botanical section. Mr. Fitch has noticed that Aphis asteris, from the situation it affects in the Essex salt marshes, must be covered by the tide eight hours out of the twenty-four ; and though as a rule the fully developed forms dis- appear in the autumn, some of them may in mild seasons be met with much later in the year. Siphonophora lactucce for instance was abundant among the inner folded leaves of lettuce at Colchester during December, 1900, and continued to flourish till its food was destroyed by the severe frosts that followed. Some authors say that all the individuals of the early broods are wingless, but this is certainly not the case invariably, for winged specimens of some species have been common at Colchester during the present spring (1901). Existing in such enormous numbers, and carrying on their operations on such an extensive scale, Aphides are generally formidable enemies to contend against ; small greenhouse plants can be easily freed from them, but large trees and crops that cover exten- sive areas do not so readily lend themselves to successful treatment, and most of the remedies recommended are costly and useless, and in apply- ing them we are in danger of interfering with nature's remedies, which are as a rule much more efficacious than ours. No tribe of insects has so many formidable enemies among other orders as the plant lice. They are preyed upon by certain of the fossorial Hymenoptera, which carry them off to their burrows as food for their larva?, and as they sting and paralyze but do not kill them the larvae are provided with a sufficient supply of fresh meat as long as they require it. Large numbers of species of Bracomder, Cbalcididce and other parasitic Hymenoptera deposit eggs in their bodies, and in this way destroy myriads of them. The larvae of the Lacewing flies among the Neuroptera, the Syrphida among the Diptera, and the Coccinellidce among the Coleoptera also devour enormous multitudes, and when a systematic attack is made upon them by the horticulturist he is far more likely to destroy his friends than his foes, as they are much more easy for him to get at, and thus he too often stops their beneficent operations in blissful ignorance of their very existence. 192
