BIOLOGY OF LIMNERIUM VALIDUM. 



87 



THE SECOND-STAGE LARVA. 



The larva after the first molt differs conspicuously from the first- 

 stage larva in respect to the soft, unarmored head, and the much 

 shorter tail appendage (fig. 38). The mouth and its parts are also 

 considerably changed. 



The head is still large and prominent and has much the same gen- 

 eral shape as in the first stage, although considerably shorter. Its 



Fio. 38. — Limneriiim ralidum : Spcond-stasje larva. Enlarged about 30 times. (Original.) 



integument is soft and pliable like that of the body. The mouth- 

 parts (fig. 39) consist of a slightly bilobed, simple labium, and two 

 strong, curved mandibles, which project downward into the large 

 funnel-shaped mouth cavity. The body is distinctly cylindrical and 

 tapers but little behind. Twelve segments in the body may be easily 

 distingTiislied, the last one of which is prolonged ventrally into a 

 short, conical tail appendage. 



Only a few larva^ in this stage were found, and 

 they were all about 2.2 mm. long. The duration 

 of this stage is probably short, perhaps not more 

 than from 5 to 7 days. 



THE THIRD-STAGE LARVA. 



DESCRIPTION OF THE FULL-GROWN LARVA. 



Vie. .'{!» — Limnerium 

 ralidum: Mouthparts 

 of second-stage larva. 



When the larva has obtained its full size and Enlarged about loo 

 leaves the host it is from 9 to 10 mm. long, and 

 pinkish white in color. It is like the usual hymenopterous type of 

 larva (fig. 40), and the body is rather deeply twelve-segmented. 

 The head is comparatively small and inconspicuous, and the tail 

 appendage, so characteristic of the first stage and still persistent in 

 the second stage, is now entirely lacking. 



The mouth parts (fig. 41) are decidedly different from those in the 

 preceding stages. They consist of strong mandibles, supported by 

 two short, longitudinal, heavily chitinized ridges, and two long, 

 transverse ridges that extend nearly to the lateral margins of the 



