256 Miscellaneous. 



duced upon the infested organism (parasitic castration &c.) are also 

 of much interest, and I hope to make them known in a future 

 communication. It is marvellous to see the infested Ti/phlocybce 

 move, leap, and fly like health^' individuals at the precise moment 

 when the Hymenopterous larva quits the sac and abandons its host 

 reduced to an inanimate skin. 



Dr. Thomas, generalizing with great sagacity the old notion of 

 the vegetable gall, has given the name of cecidia to every morpho- 

 logical manifestation caused by the local reaction of a plant to an 

 animal or vegetable parasite, whence the distinction between zooce- 

 cidicB and phj/tocecidice. It seems to me that we may emi)loy a 

 parallel nomenclature for the animal galls. I propose to call these 

 productions ihylacue. We already know a certain number of zoo- 

 thylacicp, for example the card notJii/la cue produced by the Bopyridse 

 upon the Decapod Crustacea, the entomotJnjlacice, such as the tumours 

 caused by the Cuterehrcn upon the skin of the Mammalia, or the sac 

 of Typhlocyha which we have just been considering. AVe also know 

 some jihytothylacup, the coccidial tumours of fishes, the anthrax- 

 pustule {bacteriofhylacia), &c. 



We must also distinguish from these external thylacioe the internal 

 thylacicr, such as the sacs of the larva of Tachinidse, the Entoniscidae, 

 the cysts of the TricMnce, &c. The thylacia of Typhlocyba is formed 

 by a gradual dilatation of the hypodermis, which secretes an abnormal 

 cuticle more strongly adorned with undulated striae than that which 

 covers the actual body of the insect. 



I must warn entomologists who may wish to repeat my observa- 

 tions against a cause of error which stopped me for some time. A 

 good many of the Typhlocybre of the alleys of the Luxembourg are 

 infested, not by the Hymenopterous larva above-mentioned, but by 

 a Dipterous larva, and as the latter, when mature, issues rapidly 

 from the body of its host when this is placed in a collecting-tube, it 

 gets mixed with the larvse of Hymenoptera which have also escaped. 

 One might then be tempted, knowing the habits of the Tachinidae, 

 to believe that the Dipterous larva is the producer of the gall and 

 the Hymenopterous one its parasite. 



This has probably been done formerly ; but I have been able to 

 ascertain that the Dipterous larva occurs in the body of the Typhlo- 

 cyba itself, with the head directed towards the extremity of the 

 abdomen of its host, which it distends so much as to make it 

 slightly pass beyond the wings, which is not the case in the normal 

 state. This Dij^terous larva, after issuing through the dorsal part 

 of the middle abdominal somites, becomes converted into a naked 

 pupa at the surface of the ground, and I hope shortly to be able to 

 describe the perfect insect. — Comptes Rendus, July 8, 1889, p. 79. 



