DIPTERA OF MINNESOTA. 59 



organs. This cavity is also lined by hairs, especially at the base, 

 around the anthers. The stigmas are placed above the anthers, and 

 curve over them, the anthers being surrounded by the hairs of the 

 flask. 



"Fertilization takes place in the following way: The Cecidomy- 

 id enters the throat and passes down it, the hairs being placed so as 

 to allow its free passage. As soon as it enters the flask it crawls about 

 until its back, which is laden with pollen, comes in contact with the 

 stigma, and thus fertilizes them. Upon this taking place, they spring 

 up and assume an erect position. At the same time the hairs of the 

 flask collapse and the anthers dehisce. The insect then crawling down, 

 gets the pollen upon its back. While all this has been taking place 

 the hairs of the funnel have withered up, and the Cecid or other insect, 

 laden with fresh pollen, flies away to another blossom to repeat its 

 experiences. But this is not all ; as soon as the insects are free from 

 the fertilized flower, the lip of the corolla bends over the entrance to 

 the blossom, and thus effectually stops another fly from entering on a 

 useless mission. The whole pedicel assumes a bent appearance, while 

 the unfertilized ones are erect. 



"This is, perhaps, one of the most curious adaptations that a plant 

 has undergone for fertilization by insects, and has called forth a great 

 deal of attention." 



A few larvae of this family are found in decaying wood, one species 

 has been reared from decaying tulip and hyacinth bulbs. For the 

 most part, one species will confine itself to a certain species of plant, 

 or closely allied species of plants. Note, for instance, the much 

 dreaded Hessian fly, which affects wheat almost entirely, although 

 taken on barley, and on rye sparingly. One curious exception to this 

 seeming rule is noted in the case of C. sisymbrii, which it is claimed 

 forms a gall in the spring on the barberry, and later in the season on 

 the nasturtium. It is to be noted also that the larvae of some species 

 live as guests or parasites in galls formed by other species, and some 

 live parasitically amongst plant lice. Attempts have been made to 

 classify the galls made by individuals of this family. No doubt all 

 of our readers have observed the peculiar cone-like growth on the tips 

 of branches of some of our willows (see illustrations). This is called 

 the "Pine Cone Willow Gall" and is made by a Cecidomyid very com- 

 mon in Minnesota. 



