PREDACEOUS LARV^* 95 



less pronounced wine-red coloring; the chitinous parts are brown or piceous. 

 Certain South American forms of Megarhinus are said to show an iridescence, 

 similar to mother-of-pearl. The larvae of Bancroflia also show a pronounced 

 red color of the body. 



Generally speaking the body of mosquito larvae is pale, more or less translu- 

 cent. It may be modified within the same species by a great variety of circum- 

 stances, such as age, condition of health, food, exposure to light, and the presence 

 of internal or external parasitic fungi or bacteria. The trachese usually show 

 through the integument as wavy lines of a silvery or golden luster from the air 

 contained in them. They become less distinct as the larva with approaching 

 maturity grows more opaque. The chitinous parts may be yellow, brown or 

 nearly black. Sometimes the head shows darker spots dorsally, characteristically 

 arranged. We have seen larvae in which the head was entirely yellow, others 

 with brown maculations, others entirely dark brown, all belonging to one species. 



ADAPT.ATION OF THE MOUTH-PARTS OF CULICID LARV/E TO THE 



PREDACEOUS HABIT. , 



The habit of feeding exclusively upon living organisms, principally upon 

 other culicid larvje, has arisen several times independently among the Culicid^. 

 The mouth-parts have been correspondingly modified in every case that the habit 

 has been developed. It so happens that the organ which has been modified for 

 prehension differs in the several groups. The CorethrinjB are all predaceous 

 and seize their prey with the antennae. These organs are consequently modified 

 for this special purpose, differing in the several genera. In these forms the 

 mandibles have the toothed parts well developed but the hair fringes undevel- 

 oped, being confined to a few filaments. The maxillae in all the forms known to 

 us, Eucorethra, Corethrella, Corethra and Chaohorus, are progressively reduced, 

 being slight rudiments only in the latter two genera. This is a special modifica- 

 tion in this line of descent and does not represent the condition in the general- 

 ized culicid stock. ISTo predaceous form will be found in a primitive condition 

 as the habit is secondarily acquired and accompanied by special modification. 

 The most generalized condition of the culicid larva is found in Dixa. This 

 larva is a vegetable feeder with mouth-brushes on the labrum and a coarse hair- 

 fringe on the mandibles. It is a surface feeder. The mandibles are dentate on 

 the inner side toward the base. The maxillae are quadrate and furnished with a 

 long functional palpus, comparable to the antennae in shape and size. From 

 such a form the culicid series is derived. The lowest mosquitoes. Anopheles, are 

 still surface feeders, retaining square maxillse, the palpi of which, though much 

 reduced, are still comparatively large. The square maxillse may be regarded 

 essentially as organs of mastication. They are modified in the higher forms, 

 whose manner of feeding has become more refined, into a conical or pointed 

 shape with papillse and hairs. There is, however, a tendency to the reappearance 

 of the square maxilla in the predaceous genera, in adaptation to the new habit 

 which requires more mastication. Throughout the Culicid series there is a 

 progressive degeneration of the maxillary palpi, whether the predaceous habit 



