156 THE OAK GALLS AND GALL INSECTS
Andricus trilineatus. Common. These galls are usually very
difficult to see until the insects have emerged. They may,
however, form swellings, especially when they occur on the leaf
stalk.
First appearance noted, June 11th.
(14.) Agamic Generation. IV. Andricus globuli (Htg.)
Inquilines. S. nervosus (Htg.), S. vulgaris (Htg.), and S. ruficornis
(Htg.)
Gall.
Found in the bud in September, surrounded at the base with
bud scales. Falls to the ground in October. Colour: Green,
often having some lighter spots upon it. Shape; Globular.
There is an inner gall with a large larval cavity, which is covered
with an outer green rind. This rind falls off at maturity,
leaving the woody inner gall exposed. This inner gall is
furrowed.
Imago.
Colour: Black. Antennae: Brownish. Thorax: Dull, may be pubescent;
mesonotum slightly punctured. Abdomen: Shining, ventral surface reddish
brown, darker above. Legs: Reddish brown; coxae and four posterior tibiae
infuscated. Stiff erect hairs on the fore tibiae.
(14.) Sexual Generation. IVa. Andricus inflator (Htg.)
Inquiline. Sapholytus connatus (Htg.)
Gall.
Resembles a thickened shoot. Colour: Light yellowish green
with a red apex when young, becoming brown and woody later.
The inner gall enclosing the larvae is yellowish brown, smooth
and oval, situated near the base of the cavity of the gall.
Imago.
Colour: Black. Antennae: Dark, reddish yellow towards the base. Thorax
and Head: Black, slightly shining mesonotum shagreened. Abdomen: Reddish
beneath, dark above. The male, according to Adler, has the abdomen entirely
dark. Legs: Reddish brown, posterior tibia; and coxae dark.
Account of Generation Cycle.
The flies from the A. globuli galls emerge at the end of March
or during April. When ovipositing the insect directs its
ovipositor under the bud scales, the eggs being placed in the bud
axis, one egg in each bud.