. Circular. Insects. 5. Fig. 2.—Spotted ladybird {Megilla maculata): a, Larva; 6, empty pupal skin; c, beetle, with enlarged antenna above. All enlarged. (Author's illustration.) insects produced each day, which is six, one individual would become the progenitor of 423,912 of these aphides in one season. NATURAL ENEMIES. The efficiency of natural agents in the destruction of aphides is so well known that it has been hoped that some one or more of the many species observed to attack the pea aphis would increase in such num- bers as to have the effect of limiting its multipli- cation. In spite,
. Circular. Insects. 5. Fig. 2.—Spotted ladybird {Megilla maculata): a, Larva; 6, empty pupal skin; c, beetle, with enlarged antenna above. All enlarged. (Author's illustration.) insects produced each day, which is six, one individual would become the progenitor of 423,912 of these aphides in one season. NATURAL ENEMIES. The efficiency of natural agents in the destruction of aphides is so well known that it has been hoped that some one or more of the many species observed to attack the pea aphis would increase in such num- bers as to have the effect of limiting its multipli- cation. In spite, however, of the closest observation by a number of persons, the natural enemies have been found to produce only transient relief, and this only in limited areas, as a rule late in the season after damage has been ac- complished. The present list of in- sects known to attack this aphis includes seven species of ladybirds, or "ladybugs" as they are familiarly termed,1 three species of syrphus flies,2 a lace-wing fly,3 a soldier beetle,4 and a few minute four-winged hymenopterous The ladybirds are destructive both as beetles and larvae ; the syrphus flies only in the larval condition, which is true also of the lace-wing fly. The efficiency of the syrphus flies is greatly impaired by the presence of a braconid parasite,6 which is sometimes very prevalent, almost com- pletely exterminating its hosts in many fields. Nearly all the species observed are well-known enemies of other aphides, and in fact greatly prefer as hosts the cabbage aphis and species found on weeds to the pea aphis. The spotted ladybird (Megilla maculata DeG.) and a lace- wing fly (Chrysopa oculata Say) are shown in their different stages in figures 2 and 3 respectively. In addition to the natural enemies that have already been enumer- ated, several other insects attack the pea aphis, among them a small red mite, RhyncJwlophus parvus Banks. 1 Coccinella novemnotata Hbst., Hippodamia converge
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectinsects
