. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Egg-burster of Eucephalous Fly-larvce. 375 effected by a pair of muscles which are attached to the inside of the disc and pass across to the vential side of the head. These muscles are easily seen in the perfectly transparent larva of Chaoborus {Caretlira) ; they are shown also in the accompanying diagram of the egg-burster of Theobaldia annulata. Though they almost meet on the chitinous disc, the muscles are wide apart at their ventral insertion. I have not ascertained whethe
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Egg-burster of Eucephalous Fly-larvce. 375 effected by a pair of muscles which are attached to the inside of the disc and pass across to the vential side of the head. These muscles are easily seen in the perfectly transparent larva of Chaoborus {Caretlira) ; they are shown also in the accompanying diagram of the egg-burster of Theobaldia annulata. Though they almost meet on the chitinous disc, the muscles are wide apart at their ventral insertion. I have not ascertained whether they persist beyond the first larval stage. One must suppose that the egg-burster is raised and so brought into use by blood-pressure on the relaxation of this pair of muscles. The precise form of the chitinous disc varies somewhat in the different species examined. It is relatively larger and more conspicuous in the Culicidse than in the Chirouo- midaa and Mycetophilidae, while among the Culicidse it is F3of. Simuhum austeui, Edw. Dorsal view of head of newly hatched larva, showing minute egg-Burster near posterior end of clypeus. x about 60. From a spirit- specimen. decidedly more heavily chitinised in Aedes than it is in Theobaldia or Anopheles. In Aedes it is connected by a narrow chitinous rod with the posterior part of the clypeus, the rod arising from a thickened bar in the chitin. I have not been able to detect this rod in other Culicidse or in the other families examined. The eggs of Aides have usually great powers of resistance to dessication, and pro- bably on this account have a thick chorion, which necessitates a more efficient egg-burster. The two species of Aedes examined show slight differences : the egg-burster in A. argenteus is nearer the posterior end 25*. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resembl
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