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    This bulletin describes three hackberry galls, the insects which make them, and 19 of their natural enemies in the Cayuga Valley near Ithaca, N.Y. Two galls were caused by psyllids and the third by a cecidomyiid. The taxonomy, biology, morphology, and distribution of the species are discussed.

    Fourteen natural enemies attacked the psyllid gall makers, and five fed on the cecidomyiid gall maker. However, no cecidomyiid parasites were found in psyllid galls, nor were natural enemies of psyllids located in cecidomyiid galls. Whereas most natural enemies attacked only gall makers, three were normally parasites of lepidopterous leaf miners of hackberry, and two fed on a wide range of insects other than those associated with hackberry.

    At least three parasites of the psyllid complex were secondary; two were specific to a single primary parasite, and the other fed on all primary parasites as well as the gall makers. Two natural enemies fed only on psyllid galls, but always killed the gall makers while feeding. Some parasites of psyllids fed on the gall after consuming the insects.

    One of the psyllid gall makers often incorporated itself in the larger gall of the other psyllid, a condition termed marginal gall. Parasites found in marginal galls were always the same as those found in the large galls, which is considered to be evidence that certain parasites were attracted not by host nymphs, but by the gall.

    Some primary parasites were more abundant than the others. Those whose larvae immediately fed on gall makers were more successful than other primary parasites, whose larvae began feeding after a period, of time.

    One new genus and four new species are described and methods of statistical separation are given for two closely related parasites.

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    Moser, John C. 1965. The interrelationships of three gall makers and their natural enemies, on hackberry (Celtis Occidentalis L.). New York State Museum and Science Service, Bulletin Number 402. 95 p.

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