The conopid fly Stylogaster neglecta Williston (Diptera: Conopidae) is a parasitoid with no known host. We report this species as the first recorded dipteran parasitoid of Oecanthus nigricornis Walker (Orthoptera: Gryllidae) (black-horned tree crickets). We reared field-collected O. nigricornis juveniles over several months in 2017 and found that larval S. neglecta emerged from them during late July into August. We estimated the incubation period for S. neglecta larvae to be around 30 days based on the length of time it took for them to emerge from the host and pupate (subsequently all hosts died). We documented several cases of multiple parasitism. In 2018, we dissected O. nigricornis sampled from four sites across southern Ontario, Canada and upstate New York, United States of America and found that the percentage of juvenile O. nigricornis parasitised ranged 2–39%. Further sampling will be necessary to determine whether this variation represents consistent population differences or between-year variation in parasitism.

灰头苍蝇Stylogaster neglecta Williston（双翅目：Conopidae）是寄生虫，没有已知的寄主。我们将此物种报告为Oecanthus nigricornis Walker（直翅目：Gryllidae）（黑角tree）的第一个记录的二翅类拟寄生物。2017年，我们在几个月内饲养了野外采集的O.nigricornis幼体，发现幼体S.neglecta在7月下旬至8月间出现。我们根据疏忽链球菌幼虫从宿主和化脓中出来（随后所有宿主死亡）所花费的时间估计，其潜伏期约为30天。我们记录了多发性寄生虫的几例。在2018年，我们解剖了O.nigricornis从加拿大安大略省南部和美利坚合众国纽约北部的四个地点进行抽样调查，发现寄生的黑褐O. nigricornis的百分比范围为2–39％。有必要进行进一步采样以确定该差异代表一致的种群差异还是寄生虫年间差异。