No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 3 



I beg that this may be regarded as a fault of omission and not 

 as a fault of commission. 



I would express my sincere gratitude to Prof. C. O. Whit- 

 man for his kindly guidance and friendly counsel throughout 

 the progress of my work in his laboratory at Clark University 

 during the autumn and winter, and at the Marine Biological 

 Laboratory during the summer months, of 1891 and 1892. I 

 am also indebted to Mr. S. H. Scudder for the identification 

 of several Orthoptera. 



I. The Embryonic Development of the Locustid^. 



I. The Oviposition of Xiphidium ensifernm, Scud. 



Xiphidium ciisifcnim, Scudder, a very common Locustid in 

 Wisconsin and the neighboring states, deposits its eggs in the 

 silvery napiform galls produced by Cecidoinyia gnaphaloides 

 (and perhaps allied species) on the low willows that abound in 

 the marshy lands and along small water courses. I have found 

 the insect ovipositing from the middle of August to the middle 

 of September. It thrusts its ensate ovipositor in between the 

 imbricated scales of the gall and places its eggs singly or in a 

 more or less even row with their long axes directed like the 

 long axis of the gall. The eggs are completely concealed by 

 the scales, the overlapping edges of which spring back to their 

 original positions as soon as the ovipositor is withdrawn. 

 The number of eggs deposited in a gall varies greatly : some- 

 times but two or three will be found ; more frequently from 

 fifty to one hundred; in one small gall I counted 170 and I 

 have opened a few which contained more. Sometimes as 

 many as ten eggs will be found under a single scale; when 

 this is the case, the eggs adhere to one another and are 

 more or less irregularly arranged, as if two or three insects 

 had in succession oviposited in the same place. 



The Cecidoinyia galls vary considerably in shape: some are 

 long and more or less fusiform, others are spheroidal. In the 

 former variety the scales are pointed and flat, while in the 

 latter they are rounded and have their median concave por- 

 tions less closely applied to the convex surfaces of the scales 



