. 
82 HETEROMERA. [ Metoecus. 
The life history of M. paradoxus will be found very fully dis- 
cussed in the Annals and Magazine of Natural History for October, 
1870, by Dr. Algernon Chapman, to whom I am indebted for the 
following observations :—The young larva appears to resemble the young 
campodeiform larva of Meloé , it is a little black hexapod, about 3 mm. 
in length, broadest about the fourth segment and tapering to a point at 
the tail; the head is triangular with a pair of 3-jointed antenne, 
and the legs are much like those of the larva of Meloé ; the tibie end 
in two or three claws, which support and are obscured by a large trans- 
parent pulvillus or sucker of about twice their length ; each abdominal 
segment is furnished with a very short lateral spine pointing backwards, 
and the last segment is terminated by a large double sucker similar to 
those of the legs; the history of the laying of the egg and of the way 
in which the young larva enters the wasps’ nest does not appear as yet 
to be fully understood, and, as far as I know, no wasp has been 
observed infested by the larvee of Metacus, as the Andrene are by the 
young Meloé larva; we do know, however, that when the young larva 
in the wasps’ nest finds a wasp grub suited to its taste, it makes its way 
into the interior, probably entering at the back of the second or third 
segment ; after feeding within the larva and largely increasing in size 
(3° to 4 ne ), 1t emerges from the body of its victim and casts es skin ; 
after this it becomes shorter and thicker and loses length by the 
curving forwards of the head, which is very marked in the full- erown 
larva, and does not exist before its emergence from the wasp’s body ; at this 
stage the larva is found lying like a collar immediately under the head 
of the wasp grub, and it is attached to it by the head, and appears to 
feed upon its juices; when it has reached a length of 6 mm. it changes 
its skin for a second time, and gradually the whole of the wasp larva, 
even to the head and jaws, disappears, being devoured by the voracious 
parasite ; the perfect beetles emerge about two days after the wasps in 
the same row of cells, and it is a curious fact that the wasps, which ap- 
pear to investigate everything that appears unusual in the cells, with a 
view to remove any dead pupe, are, apparently, quite as satisfied with 
a living Metecus larva as with one of their own pup#; the full-grown 
larva, as described by Dr. Chapman, is very like a Crabro or Pemphredon 
larva; it is of a whitish colour, much flattened, especially in front, with 
a very small head and with the last two segments smaller than the rest, 
the last being the smallest and apparently divided into two and 
furnished with a very distinct rounded anal tubercle ; several of the 
other segments are also armed with tubercles, which appear to assist in 
holding the wasp grub; the length is 11 mm. 
The larva of Rhipidophorus bimaculatus, F. (EHmenadia larvata, Schrank.), has 
been found in the root and stem of Eryngiwm campestre, which it perforates in a 
vertical direction; the female lays her eggs in the neck of the root, and the larva 
hatches in March; the insect, when full grown, works its way out of the stem about 
the end of June, and forms a cocoon, about the size of a nut, attached to the stem, in 
which it changes to a pupa; the perfect insect appears in July ; the habits of this 
