Lgg-burster of Eucephalous Fly-larve. 373 
In regard to the Diptera, I have only succeeded in 
tracing two published references to an egg-burster, both 
relating to the Culicide. Howard, Dyar, and Knab, in 
their ‘ Mosquitoes of North and Central America and the 
West Indies,’ say (vol. i. p. 97) :— 
“The first-stage larva may be recognized by the presence 
on the head of the egg-burster. This is situated dorsally 
on the middle of the head and consists of an oval, pale, 
depressed area, in the middle of which is situated a chitinous 
disc surmounted by a small black chitinous peg.” 
Scott Macfie (Bull. Ent. Res. vii. 1917, p. 298) says in 
regard to Stegomyia fusciata : “The ‘ egg-burster,’ situated 
dorsally about the middle of the head, is a conspicuous 
feature in the first phase”; he also gives a figure which 
shows this organ, though not in any great detail. 
In several Dipterous larvee of different families which I 
have been able to examine, tlie ego-burster has a position and 
structure similar to that indicated by the above-mentioned 
authors for the Culicidee. Itis essentially the same in Ano- 
pheles maculipennis, Aédes argenteus (= Stegomyia fasciata), 
A. (Ochlerotatus) geniculatus, Theobaldia annulata, Chaoborus 
(=Corethra) plumiccrnis, Simulium angustipes, S. austen, 
Chironomus dorsalis, Bolitophila pseudohybrida, aud Tri- 
chonta sp. In none of these cases does it resemble that of 
Pulex canis, described by Packard as “a thin vertical plate, 
like the edge of a knife.” 
Though the list given above comprises all the species 
which I have observed, it is sufficiently comprehensive to 
warrant the belief that the egg-burster will be found to be 
present in a similar form in all the eucephalous larvee of 
Nematocera, though it may not always be functional. 
In every case all trace of the structure disappears after, 
the first moult, though sometimes (at least in Chironomus 
dorsalis and Aédes geniculatus), and perhaps always, a minute 
black pigment-spot is observable under the cuticle of the 
second-stage larva in the position occupied by the egg- 
burster in the first stage. 
In an egg which is ‘about to hatch, the young larva can 
be observed (provided the shell is thin enough) moving its 
head up and down and cutting or scratching a slit in the 
shell. I have observed this process in Bolitophila pseudo- 
hybrida, aud in the newly-hatched larve of the same species 
have seen the egg-burster being raised and lowered. Pre- 
sumably this latter movemeut also took place within the 
egg, though I was not able to observe it. 
oD?) 
It would seem that the oes of the ege-burster i is 
Ann. & Mag. N. Hist. Ser. 9. Vol. iti, 25 
