25O MAINE AGRICULTURAL EXPERIMENT STATION. 1916. 



period is doubtless much more extended. In the case observed 

 (laboratory) the egg-stage lasted between 72 and 90 hours. 



Larva (Fig. 36-4, 5 6, 7). At a very early stage (2 or 3 mm. long) 

 the young larva shows the characteristics of the full grown one, seem- 

 ingly differing only in size. Full grown larva about 16 mm. long; 

 maximum width 3.75 mm., maximum height 3.5 mm. Nearly cylindrical, 

 broadest in the middle; the anterior segments forming a globose, false 

 head; the posterior segments tapering rather rapidly throughout the 

 caudal eight (about 2 mm.) of the length to the posterior respiratory 

 appendage. The latter structure terminal ; about .75 mm. long, .66 mm. 

 broad at its base, .5 mm. broad at its apex, and about .4 mm. high. The 

 double nature of the appendage indicated by moderate impressions on 

 the mid-dorsal and mid-ventral lines. 



The distal end is truncated, and the stigmal plates ornamented with a 

 pair of circular plates, three pairs of spiracles and four pairs of pal- 

 mately-divided, plumose, interspiracular hairs. The circular plates 

 occupy nearly a median position, dorso-ventrad, and are situated near 

 the median line. Each has a diameter of .085 to .095 mm. and their inner 

 margins are less than .02 mm. apart. The spiracles are roughly S- 

 shaped, each ornamented with about twenty short, rounded, lateral 

 denticles, irregular in size and irregularly distributed. The right median 

 spiracle forms an S, the left one a reversed S. In other words the dorsal 

 free end of the S on either stigmal plate is directed laterad, the ventral 

 free 'end, mesad. The interspiracular ornaments consist each of about 

 five plumose or feathered hairs arranged palmately. Some of the hairs 

 are further divided; all are united at the extreme base; and occasionally 

 two are united for some distance from the base. 



Immediately cephalad of the posterior respiratory appendage at each 

 side of the twelfth segment are three fleshy, conical lateral protuber- 

 ances, the posterior one about .75 mm. long, the others about half that 

 length, each pair connected by a prominent wrinkle across the dorsum 

 of the segment. The first four body-segments composing about the 

 anterior sixth of the body (2 or 3 mm.) is head-like globular, and 

 separated by a slight neck-like constriction from the succeeding seg- 

 ments ; with several faint longitudinal furrows on its sides. At the 

 anterior end this false-head bears a pair of small antennae, each of a 

 fleshy base, surmounted by two, minute, sub-equal, rounded nodules 

 side by side at its apex. Just ventrad of the antennae is a rounded, 

 somewhat-chitinized month-hood, concave ventrally, within which is the 

 buccal cavity. The mouth opening further guarded by a fleshy fold 

 at each side, covered with long flexuous hairs, of service in straining 

 the food. The dorsal part of the bulbous false-head is ornamented 

 with a characteristic group of black, chitinous hooks or thorns. There 

 are two large hooks about .25 mm. long on each side, situated about 

 one millimeter dorso-laterad of the mouth-hood, their bases -about .35 

 mm. apart. Extending between, and dorsad, of them are three irregular, 

 transverse rows of smaller and various-sized thorns, most of them: 



