Egg-bursler of Eucephalous Flt/'Iarcce. Ii73 



In regard to the Diptera, I have ouly succeeded in 

 tracing two published references to an egg-burster, both 

 rchiting to the Culicid;e. Howard, Dyar, and Knab, in 

 thiir ' Mosquitoes of North and Central America and the 

 West Tndiesi/ say (vol. i. p. [)7) : — 



"The first-stage larva may be recognized by the presence 

 on the liead of the egg-burster. Tiiis is situated dorsal ly 

 on the middle of the head and consists of an oval, pule, 

 dcjjressed area, in the middle of M'hich is situated a chitinous 

 dijic surmounted by a small black chitinous peg.^' 



Scott Macfie (Bull. Ent. Res. vii. 1917, p. 298) says in 

 regard to >)tegomyi(i fuaciata : "'The * egg-burster,' situated 

 dorsally about the miildle 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 larvic of different families which I 

 liave been able to examine, the eg<4-burster has a position and 

 structure similar to that indicated by the above-mentioned 

 authors for the Culicid;e. It is essentially the same in Ano- 

 plieles macid'ipennis, A'edes urgenteus (^^= Stegumyia fasciata), 

 A. (Ochlerotutus) geniculatus, Tlieobaldia annulata, Chaoburus 

 {■=Curethra) jjIuiiiic mis, Siinuliuin anguslipts, S. uusteni, 

 Cliirutwinus dorsalis, Bulitophila pseudukijbrida, and 7Vi- 

 chonta sp. In none of tiiese 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 sufHt-icutly comprehensive to 

 Avarrant the belief that the cgg-bur-ter will be found to be 

 present in a similar form in all the eucephalous larvie 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 Chirotiomus 

 dorsalis ami A'edes f/euicu/<i(us), and perhaps always, a mitmte 

 bhick pigment-spoi 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 liatch, the young larva can 

 be observed (pr<ividcd 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 liolitojiliila pseudo- 

 /n/brida, and in the newly-hatched hirvie of the same sj)ecies 

 have seen the egg-burster being raised and lowered. Pre- 

 sumably this latter movement also took place within the 

 egg, though I was not able to observe it. 



It would seem that the lowering of the egg-biirster is 

 Ann. cfc M<i(/. X. Hist. Ser. 9. Vol, iji. 20 



