Heteroecus pacificus (sexgen)

Heteroecus pacificus (agamic)

Synergus deforming-pacificus

Heteroecus pacificus [sexgen]

Host: Quercus chrysolepis

Description of Gall: (Fig. A) A conical, thorn-shaped, monothalamous or single chambered gall growing from the undersurfaces of the leaves. The leaf surface immediately above the gall is darkened and slightly depressed. Galls may occur singly or in groups or clusters that may be so numerous that the developing leaf is completely aborted with the resulting growths resembling twig galls. Often the new twigs are killed by heavy infestations. Development is quite rapid with the galls containing large larvae in late May and pupae in June. The young galls are pale red in color when they first appear but darken to deeper red or reddish-purple as they mature. Adults of both sexes begin to emerge the last few days of June and continue to appear until late July. Some of the gall clusters yield only males whereas others yield only females, indicating that certain gall clusters result from female wasps that lay eggs producing only the haploid males whereas others produce the eggs that develop into the diploid females. Male specimens outnumbered the females three to one. 

Range: La Crescenta, Pasadena, Switzer's Camp, Mt Wilson, Chilao in the San Gabriel Mountains, CA

Heteroecus pacificus [agamic]

Host: Quercus chrysolepis

 The galls produced by the parthenogenetic or agamic generation show considerable morphological variation. Some are rather slender and elongated with a tapering point, whereas others are much more robust, with a shorter point. Using the shape of the gall as a primary distinguishing characteristic, Kinsey in 1922, described several varieties of Heteroecus pacificus. During the course of this study, females were obtained from galls that varied greatly in form (Figs. B, C, D). These galls were often on the same tree and sometimes on the same branch ; however, in each instance the typical alternate generation was obtained. Some galls of H. pacificus are almost globular with little or no point whereas others are so slender that they resemble a thorn. These extreme variations were not numerous in the area that was used for this work, hence insects from these types were not used. It is significant to note that the extremely slender forms did not yield inquilines or guests whereas the more robust types housed Synergus which suggests that these inquilines influence the shape of the gall. It is hoped that future rearings and studies will help to clarify the taxonomy of this species. 

Range: La Crescenta, Pasadena, Switzer's Camp, Mt Wilson, Chilao in the San Gabriel Mountains, CA

The alternate generation of Heteroecus pacificus (Ashmead) (Hymenoptera, Cynipoidea)