{Prodotrypidae), hyperparasite of Aphidius 295 



trunk of the second segment becomes visible. In addition, two 

 short spiracular trunks can be made out on the ninth and tenth 

 segments; but these never become functional, and they disappear 

 in the later stages of development. This instar lasts from about 

 thirty-five to forty hours. 



In the fourth instar, which lasts about two days, the Procto- 

 trypid grows rapidly, and when mature measures 1-67 x -83 mm. 

 The remainder of the host is quickly consumed, and, just before 

 metamorphosis, the mid-gut opens into the rectum, and its con- 

 tents are voided into the cocoon. The larva is active and wriggles 

 about freely inside the aphis skin, aided possibly by a curious 

 caudal appendage; and by these movements the faeces, together 

 with the host's skin, are kneaded into a moist compact pellet on 

 the ventral side of the body. 



The full grown larva is yellowish white, and each segment has 

 a double row of short chitinous spines. The thorax is large and 

 broad, while the abdominal segments taper away somewhat to the 

 eleventh, which bears a short stout appendage furnished with 

 spines. The head is turned completely under the thorax, and the 

 tracheal system does not differ essentially from that of the pre- 

 ceding instar. No larval antennae nor maxillary nor labial palpi 

 seem to exist at this stage. 



Lygocerus does not produce silk, but pupates in the cocoon made 

 previously by the Aphidius inside the skin of the aphis. The period 

 of pupation is fourteen to sixteen days. When ready to emerge, 

 the imago gnaws a hole somewhere on the upper side of the cocoon, 

 and creeps out. So far, no parthenogenetic ovipositions have been 

 observed, and two broods, certainly, and possibly more, may occur 

 in the season. The life of the imagoes is generally five or six days, 

 but they may live as many as ten. Examples in captivity were 

 observed to feed on the sap oozing from cut leaves, and on honey- 

 dew dropped by the aphides, but they seemed to live as long and to 

 remain as vigorous when no food was supplied. 



