López J Manuel Perilla, Johnson Paul J, Gagné Raymond J, Boe Arvid
Insect Biodiversity Lab, Box 2207A, South Dakota State University, Brookings, South Dakota 57007, U.S.A.; Email:
Systematic Entomology Laboratory, PSI, Agricultural Research Service, U.S. Department of Agriculture, c/o Smithsonian Institution MRC-168, P.O. Box 37012, Washington, DC. 20013-7012, USA.; Email:
Zootaxa. 2015 Dec 9;4057(1):115-24. doi: 10.11646/zootaxa.4057.1.7.
Stenodiplosis spartinae Gagné new species (Diptera: Cecidomyiidae) is described from eastern South Dakota and coastal North Carolina, and compared with other American congeners. The known host plants are Spartina alterniflora and S. pectinata. The larva is a seed predator of the ovule and immature caryopsis of the host plant. Adult activity is from the early emergence of the host inflorescence through anthesis. Oviposition occurs in the floret with eggs laid under the edges of the palea and lemma. The larva apparently overwinters in dehisced spikelets in the soil among rhizomes of S. pectinata, with pupation in late spring. Laboratory emergence and field activity of the adults suggest a potentialsecond or third generation developing on late emerging inflorescences. Larval feeding does not induce external color or shape changes in the spikelet. Apparently all three instars are ectoparasitized by Tetrastichus bromi Kostyukov (Hymenoptera: Eulophidae) that was probably introduced to North America in the late 1800's and is inculcated into parasitoid guilds of several Stenodiplosis species. Resource partitioning appears to occur between the gall midge and early instars of Aethes spartinana Barnes and McDunnough (Lepidoptera: Tortricidae) that feed on maturing caryopses. The feeding of this gall midge and the moth probably account for most of the reduced seed production in both natural and agronomic populations of S. pectinata.
米草窄茎瘿蚊，新物种（双翅目：瘿蚊科），发现于南达科他州东部和北卡罗来纳州沿海地区，并与其他美洲同属物种进行了比较。已知寄主植物为互花米草和拂子茅。幼虫是寄主植物胚珠和未成熟颖果的种子捕食者。成虫活动期从寄主花序早期出现至花期。产卵于小花内，卵产在稃片和内稃边缘下方。幼虫显然在拂子茅根茎间土壤中开裂的小穗内越冬，于晚春化蛹。成虫的实验室羽化和田间活动表明，后期出现的花序上可能会发育出第二代或第三代。幼虫取食不会引起小穗外部颜色或形状的变化。显然，所有三个龄期的幼虫都被四斑溴姬小蜂（膜翅目：姬小蜂科）外寄生，该小蜂可能于19世纪末被引入北美，并融入了几种窄茎瘿蚊物种的寄生蜂群落。在瘿蚊和以成熟颖果为食的米草小卷蛾（鳞翅目：卷蛾科）的早期龄期之间似乎存在资源分配。这种瘿蚊和蛾子的取食可能是拂子茅自然种群和农艺种群种子产量降低的主要原因。
