8S THE EEPORT OF THE No. 36 



Tarsi. — The normal number of segments is five, members of the Itonididinse 

 invariably having the first segment greatly reduced. Certain genera of the Hetero- 

 pezinae have four, others three, and in Oligarces there are but two tarsal segments. 

 The claws may be simple, pectinate or dentate. They vary greatly in development 

 and the same is true of the pulvilli. 



There are other structures presenting equally significant modifications. This 

 is particularly true of the generative organs and is especially well shown in the 

 modified ovipositor which reaches an extreme development in the needle-shaped 

 organ of Asphondylia, an instrument evidently designed for the piercing of thick 

 bud tissues so that the egg may be deposited close to the growing point and in a 

 place where conditions are most favorable for the development of the young. 



It will be seen from the foregoing that the gall midges can not be counted as 

 particularly strong or prolific forms, yet they have been able to maintain them- 

 selves largely by what we term evasive adaptations, which have resulted in their 

 securing a very large degree of protection at the expense of the host plant. This 

 summary is not intended to exhaust the subject, but is presented for the purpose 

 of calling attention to a group exhibiting numerous unsolved and exceedingly in- 

 teresting biological and morphological problems. There is, perhaps, no insect 

 family better suited for the study of adaptation in numerous ways than the gall 

 midges, a large group which up to recent years has been almost ignored by 

 students. 



Explanation of Figs. 3 and 4. 



1. Antenna of Microcerata spinosa, male, showing 9 short segments. This organ la 

 shorter in this species than the palp. 



2. Sixth antennal segment of Colpodia diervillae, male. Note the greatly produced 

 distal stem. 



3. Fourth antennal segment of Prionellus gramince, male, showing the conical shape 

 and the peculiar whorls of long setae arising from distinct crenulate chitinous ridges. 



4. Fifth antennal segment of Karschomyia viburni, male, showing a binodose, almost 

 trinondose structure of the segment and the peculiar circumfili or how whorls. 



5. Seventh and eighth antennal segments of Monardia toxicodendri, female, showing 

 the general shape of the segments and the characteristic stemmed disks. 



6. Fifth antennal segment of a Rhopalomyia, female, showing the generalized type 

 of segment and the low circumfili commonly occurring in the female Itonididinariae. 



7. Sixth antennal segment of Asphondylia monacha, male, showing the low, very 

 tortuous character of the circumfili. 



8. Fifth antennal segment of the pear midge, Contarinia pyrivora, male, showing 

 the binodose character of the segment and the two well developed circumfili, the latter 

 characteristic of the bifili. 



9. Fifth antennal segment of Caryomyia caryae, male, showing the short though 

 plainly sinuous circumfili, the three on a segment being characteristic of the triflli. 



10. Fifth antennal segment of ApMdoletes hamamelidis, male, showing its binodose 

 character, the three circumfili, and particularly the greatly produced loops and setae 

 on the dorsal aspect. 



11. Sixth antennal segment of Winnertzia calciequina, female, showing the peculiar 

 horseshoe-like circumfili attached to opposite faces of the subcylindric segment, 



12. Extended ovipositor of the nun midge, Asphondylia monacha, female, showing 

 the basal pouch, the thick reversible basal portion of the ovipositor and the highly 

 dereloped needle-like terminal part. 



