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I hypothesise a specific parasitic driinide of juvenile forms of Metcalfa pruinosa , flatide that has colonized Italy and neighboring countries since the 80s.
They are small winged Hymenopterans of blackish color (the wings of the female show some lighter stripes), the females are larger in size than the males, in fact they are long up to 4-5 mm 3mm males (sexual dimorphism). The females present in the terminal part of the front legs of particular processes by which they grasp the juvenile stages of the Metcalfa which are thus directly predated by the adults of this parasitic hymenoptera (host-feeding behavior).
The life span of adults is variable, in the male it is very short (some days), while the female survives for about three weeks. Even the diet varies according to sex, in fact the male generally feeds on sugary residues (it is glicifago), while the female is both glyphous and entomophagous, feeding in fact, as well as neanidi honeydew and Metcalfa nymphs which are blocked from the forelegs and the terebra of the female of the hymen and predate. The female oviphone, within the juvenile stages of the Metcalfa, the larva developed inside the host is highlighted on the outside in the form of a sort of whitish bubo that protrudes from one side of the juvenile stage of the Metcalfa which has been parasitized.
The larva feeds on the host, which is emptied completely and, when it reaches maturity, it lurks inside it, where it completes its metamorphosis. A typical, almost transparent cocoon is produced under the residues of the devoured host, in this cocoon the cycle continues until the flickering of the new adult that can take place during the same summer or the following spring. Such ovoid and semitransparent cocoons remain generally fixed under the leaves and become a typical sign of the colonization of the Neodryinus on the infested vegetation.
Neodryinus is an entomophagus of American origin, introduced in Italy in 1987 to evaluate its effectiveness in experimental biological control programs. This introduction was successful and today this parasitic hymenoptera is well acclimatized in our environments and plays a double useful action against the Metcalfa pruinosa, predator and parasitoid of the juvenile stages.
This hymenoptera is not a useful insect with immediate impact on its victim, but it is a species that is good to introduce into the environment because it is the only one that can progressively lead to control of the metcalpha. It is possible that it is not present in some areas and it is so useful to evaluate its introduction as long as there is a minimum habitat that allows undisturbed development especially in the first year, that is, an area with fresh and persistent shrub vegetation during the summer , and obviously better if with good presence of metcalpha to facilitate the settlement of the parasitoid. During the season, from July onwards, it should be possible to observe among the metcalpha colonies, the young parasitized metcalfe and subsequently the new cocoid cocoons.
Neodryinus typhlocybae controlla:
Questo imenottero non è un insetto utile ad impatto immediato sulla sua vittima, ma è una specie che è bene introdurre nell'ambiente perché è l'unica che può progressivamente portare al controllo della metcalfa.
È possibile che non sia presente in alcune aree ed è così utile valutarne l'introduzione purché vi sia un minimo di habitat che ne consenta lo sviluppo indisturbato soprattutto nel primo anno, ovvero, una zona con vegetazione arbustiva fresca e persistente durante l'estate, ed ovviamente meglio se con buona presenza di metcalfa per facilitare l'insediamento del parassitoide.
Nel corso della stagione, da luglio in poi, dovrebbe essere possibile osservare tra le colonie di metcalfa, le giovani metcalfe parasitizzate e successivamente i nuovi bozzoli del drinide.
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