OF WASHINGTON. 265 



with soil and more or less matted leaves, the larvae of both these 

 species wandered restlessly about for several days, without show 

 ing any inclination either to enter the soil or spin up in the sub 

 stances provided. Supplying them, however, with bits of soft 

 or rotting wood, bark, and dry bits of weeds or twigs having 

 large pith, the larvae began immediately to burrow into these sub 

 stances with great industry and rapidity, the Euuras apparently 

 preferring the pith of weeds and twigs, and very soon all of them 

 had concealed themselves. This experience explains the failure, 

 which has been a common one, in the attempts to breed these 

 and other gall species, and, in connection with other available 

 records, indicates conclusively that these insects normally hiber 

 nate in bark, pith, or wood. Very rarely the dry galls of 

 their own species already deserted by other larvae are entered, or 

 they spin up between matted leaves. Other saw-flies are known 

 to enter wood to hibernate, and this habit is doubtless very much 

 more common than hitherto supposed. The larvae of Tenthredi- 

 nidae are most difficult to carry through the winter successfully, 

 and I am convinced that it is largely because the proper condi 

 tions have not been supplied. 



Relations of these facts to inquilinous species. This method 

 of hibernation has an important bearing on the validity of the in 

 quilinous species, and an examination of the records, as well as of 

 the species themselves wherever obtainable, has convinced me 

 that all the species designated as inquilinous cannot be so con 

 sidered, but are really instances where the larvae of various saw- 

 flies, including those of the true gall-making species, and others 

 which live exposed on the leaves, have entered deserted galls, fre 

 quently of the previous year's growth and of both dipterous and 

 hymenopterous origin, to hibernate, and, these being collected 

 and the saw-flies subsequently reared, the latter were very natur 

 ally described as inquilinous. All these inquilinous species are 

 due to records obtained by Mr. Walsh, a most careful and con 

 scientious observer, and in nearly every case he himself pointed 

 out the close resemblance of these supposed inquilinous forms to 

 the species with which they really belong, and the facts of rear 

 ing as recorded by him show pretty conclusively of themselves 

 that my inference in regard to them is correct. 



There are six inquilinous species of saw-flies described by Mr. 

 Walsh. Two of these belong to the genus Pontania, and are 

 synonymous with true gall-makers. (A third maybe added here 

 which Walsh referred to but never described.) Two belong 

 to other subdivisions of the old genus Nematus, the larvae of 

 which live exposed on the leaves and had undoubtedly entered the 

 galls simply to secure a convenient retreat in some instances for 



