British Bracnnidct. 225 



little less numerous than his ordinarius. The following 

 additional names of victims are from Brischke : — Ocncria 

 disjm?', L., Pijf/ferajyij/ra, Hufn., Acronycta tridens, Schiff., 

 Mclanippe galiata, Hiib., and Chesias spartiaia, Fues. 

 Cocoons white. 



iv. MiCROPLiTis, Forst. 



Forst., Verh. pr. llheinl., 18G2, p. 245 ; Eeinh., Berl. 

 ent. Zeit., 1880, p. 358. 



Maxillary palpi 5-, labial 3-joiuted. Eyes villose. Antenna; 18- 

 jointed. Mesoi^lenras impressed with a creuate fovea. Abdomen 

 sessile ; sutnriform articulation obsolete. Eadius of the fore wing 



along the belly between the legs ; the colour is yellowish white, 

 and no pubescence apjjears. — The larva of a Microgastcr differs 

 from that of most insects in undergoing several considerable 

 changes of form in the course of its growth, presenting three 

 principal stages. (1) At first, while less than 1 line in length, it is 

 a slender vermiform creature, of 12 segments, without a distinct 

 head, and destitute of the singular caudal vesicle which sub- 

 sequently appears. (2) When about 1\ lines long it is proportionally 

 much thicker, and the head becomes well defined. At this time 

 the spinning-organ may be discerned, consisting of a linear duct 

 which commences at the head, and lies parallel to the alimentary 

 canal as far as the middle, where it bihircates, and is continued in 

 two branches to the anal segment. The caiidal vesicle just men- 

 tioned is a round bladder-like body attached to the last segment, 

 and covered by a fine skin which the microscope shows to be 

 studded with points or tubercles. It appears only during the 

 middle life of the larva, becoming absorbed, like the tail of a young 

 batrachian, before the attamment of full growth, and as soon as 

 the tracheae are developed. Hence it has been supposed to be an 

 orgiin of respiration ; but this seems to leave unexplained the 

 earlier mode in which that function is performed. (3) The third 

 stage differs from the two preceding in the exhibition of tracheae, 

 and the suppression of the caudal vesicle. The mouth now consists 

 of a porrected haustellum, situated in the middle of four tubercular 

 processes, the analogues of the future palpi." — The parasite derives 

 its nutriment by sucking the adipose tissue of the victim. The 

 latter, without being lacerated, is thus subjected to continual 

 exhaustion and irritation, producing marasmus, which is at last 

 precipitated into death by the breaking up of the tracheal system 

 caused by the numerous perforations of the skin through which the 

 parasites effect their egress. — The presence of a ravenous brood of 

 Microgasters in the body of a larva of L. pini does not prevent the 

 same larva from being struck by other Ichneumons. Katzeburg 

 has detected the maggot of an Anonialon, distinguished by its 

 larger size, in the midst of these parasites: the fact is delineated 

 in vol. iii., pi. 9, ff. 23, 24. As the Anomalon takes a nmch longer 

 time to attain its full size than the Microgasters, it is probable tliat 

 the deposition of the egg of the former took place before those of 

 the latter ; imless we sui^pose the Anomalon to perish prematurely 

 by the exhaustion of its supply of nutriment. 



TRANB. ENT. SOC. LOND. 1885. PART I. (aPRIL.) Q 



