EMBIA MAJOR FROM THE HIMALAYAS. 



183 



segments, and the 10th sternum is longitudinally divided into two lobes. The mouth- 

 parts closely resemble those of the adult in their general structure. The mandibles are 

 stout and broad, but partake more of the characters of those of the female than 

 the male. 



9. The Half-grown Larva. 



During the beginning of December the larva has passed through the first half of its 

 life. Measurements of these half-grown larvae were made, and their length was found to 

 average 9 mm. The antennas at this period have 21 joints, and are of equal length to 

 the thorax. In colour the larv r a3 are chestnut-brown, with the appendages and ventral 

 surface pale. I was not able to detect any external sexual differences among larvae of 

 this age. Ten abdominal segments are present, and the last sternum is longitudinally 

 divided into a pair of symmetrical plates. These persist throughout life in the female 

 insect, but are no longer evident in the male at the close of the nymphal period. The 

 basal plates of the cerci are relatively large and well developed. They are covered by 

 the 10th tergal shield and are consequently not visible dorsally. They are in contact 

 with one another on the mid-ventral line, and appear to be serially homologous with the 

 paired plates of the 10th sternum already referred to. That they are to be regarded as 

 the representatives of an 11th somite was first suggested by Enderlein (1903, p. 430). 



The mouth-parts do not differ in any details, except in size, from those of the younger 

 larva. During the cold weather months up to March, the half-grown larva undergoes 

 very little growth, and remains to a large extent dormant. Individuals extracted from 

 their tunnels were observed to be much longer, and more sluggish over the construction 

 of new tunnels than they are at other periods in their life-history. 



10. The Male Nymph. 



The nymphal condition in the male is characterised by the presence of wing-rudiments, 

 otherwise it only differs from the larva in its greater size. Its period of duration is 

 about two months commencing during the first half of May, when the young insect is 

 from 9-9| months old. The youngest nymph observed measured 11*5 mm. in length, 

 with wing-rudiments 1-25 mm. long. At the close of the nymphal instar, examples 

 15-17 mm. in length are frequent. A nymph 15 mm. long has wing-rudiments 

 measuring 225 mm. in length. 



Viewed dorsally, the body and appendages are light chestnut-brown in colour, the 

 head and the extremity of the abdomen being slightly darker than the rest. Ventrally 

 the insect is of a much paler colour. The number of antennal joints varies from about 

 23-25, and correlated with the development of the wing-rudiments the tergal plates of 

 the meso- and metathorax have assumed their triangular form seen in the f ully-fledgeu 

 adult. 



The asymmetrical condition of the cerci and apical abdominal segments in the male 

 is acquired very late in development, and for this reason is probably a phylogenetically 

 recent acquisition. In the early nymph no indications are apparent at all (PI. 37. 

 figs. 5 & 6), but in a fully-grown nymph the 10th tergite of the adult is clearly visible 



SECOND SERIES. ZOOLOGY, VOL. XI. 29 



