548 [December 



scales of the pine-cone, but by a distinct and much larger Cecidomyia, 

 hitherto unobserved, which inhabits the very heart or centre of the 

 pine-cone, the smaller Cecidomyia being mere inquilines. (See Osten 

 Sacken apud Loew, St/nops. Dipt. N. A. p. 203.) We may also in 

 some cases get useful hints on this subject from the structure of the 

 gall itself. For instance, in many Tenthredinidous galls, e. g. .S*. ovidum. 

 n. sp., on laying them bare to their foundation, the slit cut by the saw 

 of the mother insect may be plainly seen. Hence, even if, as I have 

 actually done, we should breed a Cecidomyia from such a gall, we may 

 know that it must be a mere inquiline, because the Cecidomyidous 

 oviduct is not capable of cutting such a slit. Still, with every possible 

 precaution, mistakes will sometimes be made, as to the character of the 

 insect that really makes the gall. For example, because, from the gall 

 quercus pihdse Walsh, I had bred % 9 of an Inquilinous Cynipide, I 

 jumped to the conclusion that the gall itself must be the work of some 

 unknown Psenidous Cynipide. {Proc. Ent. Soc. Phil. II. pp.481 — 2.) 

 Whereas I have since become aware that it is the work of a Cecido- 

 myia known at present only in the larva state, and that it had been 

 briefly described, but not named, by Osten Sacken. {Syn. Dipt. JV. A. 

 p. 201.) No other instance is on record, as Baron Osten Sacken has 

 obligingly informed me, of a true Cynipide being inquilinous in a Ceci- 

 domyidous gall. 



Some groups of insects that are commonly inquilinous in galls have 

 no true gall-making insects belonging to the same family as they do, of 

 which case I believe that we find an example in the Coleopterous Cur- 

 cidionidse. (See below under No. 15.) But the great majority of them, 

 e. g. the inquilinous Gall-flies, the inquilinous Saw-flies, and the inqui- 

 linous Grall-gnats, have many true gall-making species belonging, not 

 only to the same family, but in the case of the Grall-gnats and Saw-flies 

 even to the same genera, viz. Cecidomyia and Nematus, that they them- 

 selves belong to. Hence an observation of Osten Sacken's with regard 

 more especially to the Gall-flies, which I formerly quoted and relied on, 

 that " it seems hardly probable that species of the same genus should 

 sometimes be true Gall-producers and sometimes Parasites [i. e. inqui- 

 lines]" must be taken cumgrano salis so far as it may apply to the Gall- 

 gnats and Saw-flies, though it seems perfectly correct as limited to the 

 Gall-flies. {Pi-oc. Ent. Soc. PhU. I. p. 49.) What is very remarkable 



