424 



NATURAL HISTORY OF ARTHROPODS. 



FIG. 531. Larva pupi- 

 gera of Eristalis. 



FIG. 532. Syrphus meso- 

 grapta politus, enlarged. 



Pacific. The larvae, as in Mallota and some other species of the family, are very 

 curious creatures. They are ovate in shape, somewhat elongate, with seven pairs of 

 abdominal legs below, each of which terminates in, a booklet ; posteriorly they end 



in a long, slender tail, composed of two joints, the last of which 

 slides within the preceding one like the joints of a telescope. 

 This curious organ enables them to breathe from the surface 



O 



while lying snugly concealed in mud or in outhouses, where 

 they feed upon decaying vegetable or excrementitious matters. 

 This peculiarity of structure has given them the name of " rat- 

 tailed larvae." Their skins are very tough, whence conies the designation of tenax. 



The pupal envelope of the rat-tailed larvae is ellipsoidal in shape, with the tail bent 



over the body. 



Interesting also are the habits of members of the genus Syrphus, of which there 



are about twenty-five North American species. The flies are usually less than a half 



inch in length, very prettily banded with yellow, and, like many 



others of the family, are remarkable for their rapid motions in the 



air, and the ease with which they hover over flowers. The larvae 



are cylindrical maggots, without a head, and the mouth-parts 



consisting of from two to four outwardly-bent booklets. The 



eggs are deposited by the female upon plants infested by plant- 

 lice. The young larvae as soon as hatched crawl over the stems 



and leaves till they come in contact with the Aphides, which 



they pierce with the booklets and, holding aloft, suck out their 



juices, to the number of a hundred or more daily. When ready 



to undergo their transformations they attach themselves to the leaves, and the larval 



skin contracting forms an oval puparium or larva pupigera. 



Another interesting group in their early forms are the species of Microdon. The flies 



are usually dull colored, rather slow 

 in flight, and found on borders of low 

 woodlands. They can generally be 

 recognized by the presence of a pair 

 of spines on the scutellum, and by 

 their antennae being elongated. The 

 larvae show a strange resemblance to 

 certain shells, so much indeed that 



twice have they been described and named as species of molluscs! 

 The larvae of J2accha, /Sphcerophoria, Pipiza, and 



Paragus are also known to feed upon plant-lice. The 



larvae of many species live in decaying wood, in the 



stems and bulbs of plants, under bark, in water, and 



about ants' nests, all of which are characterized by the 



stigmata being confined to a single or double breathing- 

 tube of variable length at the hind end of the body. 

 Mallota posticata, here figured, is black, thickly 



covered with black and yellow pile ; the larvae and 



pupae are found in old trees. Pipiza radicicm is a 



small fly of a uniform dark metallic color ; its larva lives underground, and feeds upon 



the apple-root lice (2?riosoma pyri) and the grape-root lice (Phylloxera radicola). 



FIG. 533. Microdon globosus; a, larva just before pupation; 

 b, front view'of pupa case; <-, larva pupigera. 



FIG. 534. Mallota posticata; 

 a, larva pupigera. 



