18 BULLETIN 1487, U. S. DEPARTMENT OF AGRICULTURE 
been reared as a hyperparasite. Fiske (9) has recorded it from sev- 
eral primary parasites of Malacosoma americana. 
OPHIONINAE 
MESOCHORUS VITREUS WALSH 
Species of this genus have often been reared from the cocoons of 
various Braconidae and Ichneumonidae, sometimes in large num- 
bers; but the single species obtained from Apanteles melanoscelus at 
the gipsy-moth laboratory has appeared very infrequently. Despite 
its unimportance as an enemy of this Apanteles, however, its unusual 
habits and manner of development deserve some comment. Gat- 
enby (12) has called attention to the indirect manner of attacking 
its host exhibited by Mesochorus; but he did not actually observe 
oviposition, finding the parasites exceedingly timid under confinement. 
His statement that the egg of Mesochorus is deposited within the 
body of the primary parasite while the latter is still inside its host 
probably holds for all the species of this little known group, the 
Mesochorini. This manner of attack was observed in the case of 
the species parasitizing Apanteles melanoscelus. ‘The following state- 
ments briefly describe the procedure as noted in several instances. 
When a gipsy-moth larva, which had been attacked by Apanteles 8 
or 10 days before, was introduced into a vial containing a female of 
Mesochorus, the hyperparasite instantly became greatly excited. 
Her wings, which were spread and slightly elevated, vibrated in- 
tensely and continuously. In a few moments she mounted the 
caterpillar and at once inserted her ovipositor in one of the posterior 
segments. After some probing about inside the larva the ovipositor 
was finally inserted to its full length, held there quietly for a moment — 
or two, and then withdrawn. There were several more insertions of 
the ovipositor in the various parts of the body of the same caterpillar, 
the parasite remaining on the larva 8 or 10 minutes. Throughout 
the entire procedure the wings and antennae of the hyperparasite 
kept up an incessant vibration. Dissection of the caterpillar and of 
the Apanteles larva inside it showed that a very tiny egg had been 
deposited within the body of the immature Apanteles larva. 
The early development of the Mesochorus is slow, the Apanteles 
being permitted to complete its growth, and to emerge from its host 
and form its cocoon before being destroyed by the hyperparasite. 
This is one of the comparatively few secondary parasites that are 
endoparasitic. 
CHALCIDOIDEA 
CHALCIDIDAE 
HALTICHELLA XANTICLES WALKER (?) : 
This species of Haltichella, doubtfully determined as xanticles by 
Gahan, has been occasionally reared from cocoons of Apanteles melan- 
oscelus in Massachusetts, but only in very small numbers. It 
appears to be of little or no significance as an enemy of that primary. 
The small amount of laboratory work carried on with it indicated 
. that Apanteles is not an especially desirable host; for only 5 out of 
34 cocoons exposed individually for periods of two to four days were 
attacked. There are evidently two, and sometimes three, generations 
iti int 
