254 Acarology 



Larvae. (The taxonomy of trombiculids is based primarily on the 

 larvae.) The cheHcerae have two segments; the basal segment is stout 

 and muscular while the distal segment is a sclerotized, curved blade 

 with or without projections called teeth. The palps have five segments; 

 the basal segments are fused along the midline and have a median, 

 anterior, laminar projection that extends beyond the basal segment of 

 the chelicerae and a pair of lateral wings or galeae that curl dorsal 

 about the chelicerae and bear a seta on each side; each basal segment 

 also bears a seta posterior to the junction with the palpal femur. The 

 second palpal segment or femur bears a single seta; the third or genu 

 bears a single seta; the fourth, or tibia, has three setae; one is dorsal, 

 one lateral, one ventral, and there is a terminal palpal claw. The fifth, 

 or tarsus, articulates ventrally with the tibia and opposes the palpal 

 claw in thumblike fashion. It bears several setae (usually eight), the 

 basal one of which is a striated sensory seta. The body is usually red 

 but may be almost colorless; it bears a dorsal plate or scutum at the 

 level of the anterior two pairs of legs, usually two pairs of eyes that 

 flank the scutum, several rows of dorsal setae, several rows of ventral 

 setae, occasionally a posterior plate or a posterior group of specialized 

 setae, a ventral anus, three pairs of legs, an urstigma or sclerotized pit 

 associated with the posterior distal angle of coxa i, and at times a pair 

 of tracheal trunks that open through stigmata in the region of the 

 gnathosoma. The scutum bears from three to six marginal scutal setae 

 or infrequently more, and a pair of pseudostigmata from which the 

 sensillae or pseudostigmatic organs arise. The legs are composed of 

 six segments if the femur is undivided and of seven if the femur con- 

 sists of a basifemur and telofemur. 



Wharton 1947 recognizes four subfamilies based on the larval 

 morphology. 



Key to the Trombiculidae 



1. First pair of legs with seven segments 2 

 All legs with six segments; two setae on coxa i Leeuwenhoekiinae 



2. Legs n and ni with seven segments 3 

 Legs n and ni with six segments Walchiinae 



3. Paired, anterior, submedian, scutal setae and/or anteriormedian 



scutal projection Apoloniinae 



Not as above Trombiculinae 



