1913] 
Burrill , The (limit Midge, Chironomus plumosus. 
141 
fragments to conceal themselves.” Earlier observations of Cox 
(1878, 261-2) disagree with this, for, after criticising all older 
drawings for incorrect number of segments and the notion that the 
four prolegs were air-tubes, he says that “the larva keeps always 
under water, never coming to the surface for air. It generally 
remains concealed, and only when disturbed, or when seeking a 
fresh resting place, is it seen swimming about with that peculiar 
writhing motion which everybody has observed.” The statement 
is inexact as the frequency of these larvae in plankton has been 
studied by Kofoid (1908, pp. 285-6). Miall goes on to show that 
despite the protection afforded by their hiding tubes, the larvae are 
hampered by such enclosures in stagnant water from proper air 
supply, unless they make these swimming trips to the surface. 
Miall (1900, 130) concludes that “the thin-walled and transparent 
appendages near the hinder end of the body are probably of spe¬ 
cial service in taking up dissolved oxygen. The tracheal system 
is rudimentary and completely closed, and hence gaseous air can 
not be taken into the body. The dissolved oxygen, procured with 
much exertion and some risk, must be stored up within the body of 
the larva, and used with the greatest economy. It is apparently 
for this reason that the larva of Chironomus contains a blood-red 
pigment, which is identical with the haemoglobin of vertebrate 
animals.” This oxygen-carrying haemoglobin occurs only in such 
Chirnomid larvae as exist at the bottom and burrow in the mud, 
as C. dorsalis, C. plumosus, etc. Several points needing further 
study on both living and dead larvae are suggested bv the previous 
review and must be dropped at this point in the present paper. 
The larvae make several moults, being observed from May to 
October (Higginson, 1867, 174, for the year 1865). This, as Gar- 
man surmises (1896, 155-6) indicates an overwintering larva. 
Pupal Life and Emergence of Imago. —Later the pupae may 
come to the surface to permit emergence (Osborn 1896b, 30) of 
the adult, though the pupa of plumosus swims about in the larval 
case (Johannsen, 1905, 187). 
Higginson (1867, 175) and Cox (1878, 263) note the quick 
emergence of the adult. The latter says, “This wonderful trans¬ 
formation is performed in less time than a man takes to change 
his coat. When the pupa comes to the surface of the water, the 
