Martirano and Schoo and Ruge have noted the occurrence of flukes in the Anophelince. Thus Martirano found that in May, 1 to 20 per cent., but in June, 50 per cent., of A. maculipennis contained encysted flukes. These were found free in the stomach and esophagus, and also in the walls of the former and apparently also in the salivary gland.
They were actively motile, and when pressed out of the cysts, they measured 1.3 mm. long by 0.3 mm. wide. Two suckers and the genital organs were observed. Schoo in Holland and Ruge in Germany have confirmed this, and by Christophers and myself flukes have also been observed in dissections of West African Anophelince. It is probable that more than one species of fluke will be found. Whether these flukes are human or avian, as suggested by Dr. Brandes, remains to be seen, and it remains to be found out whether the larval stages of these flukes are passed in the larva and nympha of the mosquito and what their further life history in the mosquito itself is.
We have noticed the occurrence, in the ova, of Sporozoa, and Grassi also describes such and others in the body cavity. We should mention here the parasites described by American authors in the esophageal diverticulum, etc., of Stegomyia, which probably belong to the genus Nosema. They are a common occurrence in this genus.
Johnson, in Massachusetts, records the finding of gregarines in A. maculipennis. They were found on the outer surface of the "stomach"; also on the Malpighian tubes, and even in the salivary gland; they varied in size from 12 to 80 p. They are said to resemble malarial oocysts in appearance. Gregarines also occur in the gut of larvse.
They are not uncommonly met with in the gut (hind gut especially). Leger has described the developmental stages of a flagellate which he has called Crithidia fasciculata; at first like a grain of corn in appearance, it develops into a trypanosome like body. It is possibly a 'developmental stage in the mosquito of some protozoon.
Perroncito describes an organism resembling Leptothrix buccalis, which he considers to be pathogenic to the mosquito.
They occur on Anophelince, but also on other Culicidce. They are Acarina?., among which have been identified Tyrogliphus siro, Chryletas eruditus, Gamasus sp., and hexapocl larva? of Hydrachnidce, some of these belonging to the genera Hydrodroma or Nescea.
The head is composed mainly of the two large compound eyes, which, dorsally, are separated by an area bearing a tuft of hairs (in Anopheles), but ventrally they are separated only by a narrow line. Looking at the head from in front, we see that in the space between the eyes are the large, swollen basal joints of the antenna?, and below these the centrally placed prolongation forward, the clypeus, with the labrum epipharynx; and below it again the labium. The head is joined to the neck by a membranous neck in which lateral chitinous plates occur. The portion of the head lying behind the eyes is the occiput, while behind this it is termed the nape, or cervix. The space between the eyes and antenna? is the frons, while the part connecting this with the occiput behind is the vertex; that part of the head that lies beneath the eyes on either side is the gena.
The antennce arise from the frons. They consist of 15 segments in A. maculipennis: the first segment is extremely small; the second globular, and contains a complicated auditory organ; then follows the third segment, which is larger than any of the others. From the proximal end of each segment arise a number of hairs arranged symmetrically around the segment. In the male there are 16 segments. On the fourth to the fifteenth segments occurs that arrangement of long hairs in whorls which gives the male antenna? their characteristic plumose appearance. These whorls are 12 in number. They arise from the antenna? in two half rings, each consisting of about 30 hairs.
Passing through the head (of A. maculipennis) are two tubes, which open by a slit like trumpet orifice anteriorly between the margin of the eye and the side of the clypeus; posteriorly they open below the origin of the neck near the ventral border. They are probably hollow apoclemes, serving for the attachment of muscles. The head is connected with the thorax by a thin neck, which bears laterally two chitinous plates. These approach each other dorsally, and ventrally each sends out a process to meet but not to join each other. The posterior ventral portion of the neck lying in front of the prosterna is thin, permitting one to see the blood passing through it.
The thorax consists of three parts: prothorax, mesothorax, and metathorax. The main part of the dorsal surface of the mesothorax constitutes the scutum. Behind this there is a well marked ridge, constituting the scutellum. Behind this is a triangular, shield like portion, curved on its upper surface, the postscutellum, extending backward as far as the first abdominal segment. We have already referred to its importance in classification from the characters of the hairs or scales found on it or from the absence of any covering. Whether any of the metathorax appears dorsally is doubtful. A small sclerite, however, appears to exist posterior to the postscutellum, between it and the first abdominal segment. Similarly the prothorax is not represented dorsally. The homologies of the parts constituting the thorax are a matter of considerable dispute. It will suffice here to note the structures known as the patagia. They are situated on either side of the base of the neck. They limit, laterally, the thin ventral area of the neck. They are sausage shaped bodies, situated on a pair of freely movable sclerites. These sclerites are continued backward as rod shaped bodies almost as far as the main thoracic spiracle. Posteriorly this area is bounded by the origin of the first pair of legs (prothoracic). Nothing is known certainly as to the function of the patagia. The episternum and mesosternum form the main lateral surface of the thorax; the wings arise between the scutum and the episternum; the mesosternum also bears a trilobed process, with which the wing articulates when drawn forward. From the episternum of the metathorax arise the halteres or balancers, the homologues of a second pair of wings. Here also is situated the second thoracic spiracle.