784 



THE. DIPTERA 



The duration of the egg stage has not been well defined. Nuttall 

 and Shipley give two to three days for Anopheles maculipennis, but 

 it is probable that it is shorter in the 

 tropics. The appearance and grouping of 

 the eggs are quite different in the Culic'nae, 

 as will be mentioned later. 



The larva escaping from the blunt 

 anterior end of the egg by the shifting off 

 of a piece like a cap from the rest of the 

 shell is seen to consist of head, neck, and 

 abdomen. 



When first hatched the head is very black, 

 but later on it becomes lighter in colour, and 

 shows characteristic markings. .At the back of 

 the head there is a little notch, and from this a 

 V-shaped dark line opens forwards, formed by 

 two diverging bands of chitin, arranged along 

 which are patches of pigment, which give rise 

 to the characteristic markings. There are two 

 large compound eyes, behind each of which lies 

 a single eye-spot, or ocellus. 



The antennae are conspicuous rod-like bodies 

 ending in two leaf-shaped appendages, between 

 which is a branched hair, while another hair of 

 specific importance arises from a papilla situated 

 at the junction of the proximal and middle 

 thirds. 



Between the roots of the antenna and projecting 

 forwards there is a smooth, shield-like area, the 

 clypeus, which carries four or six hairs, which are 

 also of specific importance. Two of these hairs 

 (internal clypeal hairs) arise anteriorly near the 

 middle line; external to these lie the external 

 clypeal hairs, which arise from the outer angle 

 of the clypeus ; and behind them lie the posterior 

 clypeal hairs. Sometimes there is a basal hair 

 external to the antennae. 



The mouth parts consist of two large feeding- 

 brushes, two maxillary palps, two mandibles, and 

 on the ventral median line the under lip of 

 Meinert, a conical chitinous structure, and a 

 snout-like process covered with hairs projecting 

 between the brushes. 



The thorax is large, increasing in size as the 

 larva grows older. It has numerous hairs, and 

 sometimes a pair of the palmate hairs presently 

 to be described. 



There are nine segments in the abdomen, of which the eighth is characterized 

 by possessing the openings of the tracheae, and the ninth by possessing four 

 large papillae, and hairs projecting downwards and backwards. The first two 

 segments possess a pair of large feathered hairs on each side, the third a single 

 hair on each side. The others do not possess these hairs. Certain of the 

 abdominal segments have small, fan-shaped hairs, called ' palmate hairs,' fixed 

 by a short stalk on the outer side of the dorsum of the segment. Each of these 

 consists of nineteen to twenty leaflets, which are capable of closing and opening 

 upon the stalk like a fan. These hairs are rudimentary in the freshly hatched 

 larva, but in the adult they are well marked, and have been used for purposes 

 of classification, according to the variations in their number and position, and 



Fig. 388. — Larva of 

 Anopheles maculipennis. 



(After Nuttall and Shipley, 

 Journal of Hygiene.) 



I , Internal clypeal hairs ; 



2, external clypeal hairs ; 



3, antennae; 4, head mark- 

 ings; 5, thorax; 6, abdo- 

 men; 7, palmate hair; 8, 

 stigmatic siphon; 9, last 

 segment. 



