with notice of a new Genus of Diptera. 387 
Phytomyza of Meigen, of which many of the species in their 
early stage are known to feed on the parenchyma of leaves. 
Having traced its states as larva, pupa, and at length a perfect 
fly, I have been enabled to ascertain the characters of each ; and 
these, as I am not aware of the field being pre-occupied, I shall 
proceed to detail; and although description 1s often a barren re- 
gion to travel through, some interesting features of its ceconomy 
will occur at intervals to lighten the footsteps and reward perse- 
verance. 
The /arva is minute, of a pale glassy green, with the interior 
darker from the colour of its food ; it gradually tapers away be- 
hind and is truncate at the tip, but widens towards the front, and 
is then rather suddenly brought to a pot; the segments are 
regular, distinct, the edges rather elevated, crenulate ; about four 
or five of the anterior ones are protuberant on the sides, the 
third being the most prominent ; the first is provided with two 
bent black oral hooks, which unite interiorly with an apparatus 
connected with the muscles which put them in play ; [the two fore 
spiracles have been omitted to be noticed, but they are probably, 
as in other species, situated behind the head, above;] the pos- 
terior end is shaped like the stern of a boat, and is furnished 
above with two projecting, white spiracular processes, which are 
barbed hke fish-hooks ; the anus is a slit at the tip, between two 
tubercles. Length 2 line. It is by means of the hard oral 
mechanism that it executes its pretty workmanship, which it 
does, while lying like a true miner, on one of its sides, by a 
rapid and continuous rasping or “raking” of the green matter 
indispensable to it as food. I have not ascertained when it first 
commences its proceedings, but on the 13th of August I could 
only detect a single specimen in the larva state. Usually a leaf 
is tenanted by only a single occupant; but there are instances 
when two have obtained possession, and then the space from 
which the colour is discharged is proportionally enlarged, and 
the convolutions are considerably more tortuous. Upon ar- 
riving at a condition suitable to a change of state, which de- 
pends greatly upon the quantity and quality of the food that 
remains to be supplied, the larva leaves the side of the leaf to 
which it has hitherto been confined, cuts through the pulpy part 
of the inferior membrane, till it has reached the lower cuticle, 
through which it thrusts the tips of its posterior spiracles as well 
as those of its head, and in this position becomes converted into 
a small light-coloured pupa, the case being formed of the indu- 
rated skin of the larva. It has the instinct almost invariably to 
fix itself alongside of the midrib or one of the secondary fibres ; 
perhaps being induced to this by the obstacles they present to 
its progress in mining ; and the case being covered with the thin 
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