Studies on the orange wheat blossom midge, Sitodiplosis mosellana Gehin II. The larval life in the ears of wheat
Young, Bainley; Lee, C.C.; Woo, S.M.
Acta Ent Sinica 9(2): 116-124
The larvae of orange wheat blossom midge inflict damage on the kernels of wheat. However, since their habitats are concealed, our knowledge of their development and behavior is meager. The present paper deals with their larval life on the kernels of wheat in the suburbs of Shanghai. The results may be briefly enumerated as follows Three instars are definitely known in the larval stage and they may be easily distinguished by their caudal processes. The 1st instar is metapneustic in the respiratory system, while the 2d and the 3d instars are peripneustic. The sternal spatula, the characteristic thoracic armament in the larvae of the family Cecldomyidae, appears in the last instar. The 1st 2 instars are active in feeding and growing: the 1st lasts 4-5 days and the 2d, 5-8 days. The 3d rests upon the kernel within the exuvium of the 2d and takes no nourishment from the kernel. The occurrence of larvae on a single kernel in the suburbs of Shanghai are most solitary in distribution, just as those already observed by Barnes in England and by Wallengren in Sweden. The frequencies of occurrence in 1954-1957 were analyzed with respect to the levels of population. The higher the level of population in the field, the greater the number of kernels injured. The damage to wheat grains is so great that even a single larva would destroy the entire grain. A high percentage of destroyed grains (66.2%) each had a single larva in 1954. It is evident that the degree of damage is not primarily determined by the number of larvae feeding. The time of invasion may be of prime importance. Histological sections of the attacked kernels give valuable hints about the type of injury by the larvae of this midge, and the point of attack is also vital when it comes near the ventral furrow of the grain.