TAXONOMY OF MUSCOIDFAN FLIES — TOWNSFND ]t) 



solidly advance our knowledge of the subject than the careful and 

 painstaking study and rearing of the early stages. It is a most 

 promising and inviting field, and one whose problems are intimately 

 woven w r ith subjects of broad biologic significance. 



It may be pointed out that the well-known promiscuity of ovi- 

 position with reference to hosts in the Muscoidea is another evidence, 

 and a necessary result, of the geologically recent evolution of the 

 superfamily. The Microhymenoptera are of far more remote evo- 

 lution, as evidenced by the fact that each genus is restricted to a 

 group of hosts. Microhymenopterous parasites bred from host 

 larvae belonging to different families may safely be pronounced off- 

 hand to belong to different genera. This demonstrates a fixed habit 

 of oviposition that has endured through a long period of time. No 

 such fixed habit is to be found among those Muscoidea parasitic 

 upon lepidopterous larvae, or among any of the superfamily except 

 the CEstridae. 



It has been alleged that much of the so-called synonymy in this 

 superfamily, as it stands in the Aldrich Catalogue, is due to a mis- 

 guided erection of species on stunted specimens developed from 

 underfed larvae, through a lack of acquaintance with the breeding 

 habits of the species. It is well known to all students of the 

 Muscoidea that the females sometimes, if not frequently, carry the 

 act of oviposition to an extreme, ovipositing upon larvae that are 

 already overstocked with eggs. This has been observed and recorded 

 in a number of instances. It has been observed at the Gipsy Moth 

 Laboratory of the Bureau of Entomology in Massachusetts that 

 tachinids would oviposit at times upon larvae covered with eggs, 

 while masses of unstocked larvae were abundant close by. Some of 

 the unmolested larvae were dissected and found unparasitized. This, 

 moreover, was in the open, outside the breeding cages. However 

 puzzling this may seem, it is certainly unsafe to draw conclusions as 

 to habits from observations made in the gipsy moth area, since the 

 equilibrium of the various forms is in a state of extreme unrest. 

 This is due not only to the enormous increase of comparatively 

 newly introduced host elements in the fauna, but also to the more 

 recent introductions of new parasitic species, both tachinid and 

 microhymenopterous. These agencies have so disturbed the balance 

 between species that the resultant conditions have become highly 

 artificial. Similar conditions could hardly arise except through 

 man's interference. Had the gipsy and browntail moths and their 

 parasites spread into Massachusetts from a contiguous area, the 

 change of equilibrium between them and the resident fauna would 



