1920 .] 
Natukal-histoky Notes. 
117 
NATURAL - HISTORY NOTES. 
Metamorphosis of the Fly Exaireta spiniger Schiner, by J. G. Myers. 
As the metamorphosis of this beautiful and conspicuous fly has not 
hitherto been recorded, the following note may be of interest. 
The egg I have not yet found, but the larva, of which a sketch is 
appended, has been taken in considerable numbers, during July and sub¬ 
sequent months, amongst rejected seed potatoes 
in an advanced state of decomposition, when 
practically nothing remains but skins and fibrous 
material, Muscid larvae having accounted for the 
softer portions of the tubers. 
The larva, which is not quite fully grown in 
July, when this description was taken, presents 
a very flat appearance, with a rough, brownish- 
grey, strongly chitinized envelope, the surface 
usually fouled with dirt, but the segmentation 
very pronounced to sight and touch. The four 
anterior segments are capable of considerable 
retraction. Progression is effected by means of 
rugosities on the ventral surface, the edge of 
each body-segment being thickened. The larva 
is extremely sluggish. 
The dimensions are as follows: Length, 
11 mm. ; maximum width, 5 mm. ; maximum 
thickness, 1*5 mm. 
The pupal instar, passed within the apparently 
unchanged larval integument, among the debris 
of the larval food, lasts until the following summer, 
when the imago emerges. 
A similar Stratiomyid larva, taken among debris at the roots of spear- 
grass on Mount Alpha, Tararua Ranges, may prove to be the same species 
living under more natural conditions. 
I am indebted to Mr. D. Miller for the identification of the imago and 
for much other assistance. 
Note on a Habit of the Chiton Cryptoconchus porosus (Burrow), by 
Miss M. K. Mestayer. 
The members of the order Polyplacophora, or mail-shells, are generally 
considered to be vegetable feeders, but this summer I have had proof 
that at least one member of the order, Cryptoconchus porosus (Burrow), is 
decidedly fond of a diet of spawn. 
Early in November, 1919, a coil of spawn was deposited on the side of 
my aquarium, probably by a small Siphonaria, but before there was a 
chance of its hatching a specimen of C. porosus found it, and I saw the 
spawn being rasped off and swallowed. Then, on the 18th January, 1920, 
I found another specimen of the same species on a rather large coil of 
spawn I had placed in another aquarium at the Dominion Museum. It 
was left undisturbed, and in three days’ time every trace of the spawn was 
cleaned off the rock. , 
Larva of Exaireta spiniger, 
dorsal aspect. 
