ISEPEOLINI

ROZEN, JEROME G., 2003, Eggs, Ovariole Numbers, and Modes of Parasitism of Cleptoparasitic Bees, with Emphasis on Neotropical Species (Hymenoptera: Apoidea), American Museum Novitates 3413, pp. 1-36 : 10-12

ISEPEOLINI

Most immature stages of Isepeolus have been known for many years ( Michener, 1957; Lucas de Oliveira, 1966; Rozen, 1966, 1991, 2000a) and recently the mature larva of the sister genus Melectoides was described ( Michelette et al., 2000). The first instar of Isepeolus viperinus (Holmberg) has tremendously elongate curved mandibles, clearly indicating that it is hospicidal. However, unknown were characteristics of the egg and whether the female enters open host cells that are still being provisioned or whether she introduces her eggs into cells that have been previously sealed by the host. Claude­Joseph (1926) reported that female Isepeolus oviposits on the provisions. Roig­ Alsina (1991) suggested that the eggs might actually be hidden in the host cell, thus implying that the cell is attacked before cell closure. His suggestion was based on the female’s modified sixth sternum, convergent with nonhomologous modifications in the Protepeolini and Nomadinae, which are known to enter open cells and hide their eggs in the cell walls.

On a fieldtrip to Chile in October and November 2000, I collected and preserved in Kahle’s solution the cellophanelike linings of the cells of colletines from holes in vertical banks in Limari and Elqui provinces in the hope of recovering information about isepeoline eggs and how they are introduced into the host cells. Adults of both Isepeolus luctuosus and Melectoides triseriatus were collected at the nesting sites. I found three eggs of I. luctuosus on the cell linings of either Colletes or possibly Mourecotelles . (Subsequently, the partial remains of a chorion were also recovered from a cell lining, collected dry, containing a vacated cocoon of I. luctuosus ).

Two eggs (one of which had hatched) were side by side in one cell, and the other was in another cell. Each cell contained a cast, darkly pigmented head capsule to which was attached the transparent, clear cast body skin of a first instar. The egg from the other cell had not hatched and presumably had been killed by the first instar, whose chorion was not detected. The chorion of the hatched egg had split anteriorly and longitudinally along one side at the time of eclosion, and the first instar presumably then killed the unhatched egg. 2 The cast first­instar exoskeletons were split longitudinally along the dorsal midline,

2 The presumption that the intact eggs of Melectoides triseriatus were killed by the first instars of the same species is based on the fact that with many cleptoparasites, a first instar will kill the eggs or first instars of others of its kind that it encounters. I looked for puncture marks or tears in the chorions of the two eggs but was unable to see external damage.

starting just behind the head; the head capsule of each was completely intact, as were the mandibular apodemes.

The identification of the cleptoparasite as Isepeolus luctuosus and not Melectoides triseriatus is based on the following: (1) the eggs were associated with distinctive first­instar head capsules morphologically nearly identical to those of I. viperinus ( Michener, 1957; Lucas de Oliveira, 1966; Rozen, 1991), thereby indicating they belonged to the Isepeolini ; (2) adults of M. triseriatus and I. luctuosus were the only isepeolines collected on that trip and a subsequent one to the two provinces in October 2001; and (3) on the second trip, females of M. triseriatus were preserved for dissection, and a colletid cell containing a pupal I. luctuosus in a cocoon had the shed head capsule preserved in the fecal material surrounding the cocoon. The head capsule was identical to the two recovered with the eggs the previous year. Furthermore, mature oocytes of M. triseriatus have a distinctively thick dorsal chorion unlike the thin one of I. Luctuosus , and they lack the roughened posteroventral patch characteristic of eggs and mature oocytes of I. luctuosus (see diagnosis under Description of Mature Oocyte of Melectoides triseriatus , below, for other features distinguishing the oocytes of the two species).

The only inconsistency between the eggs and mature oocytes of Isepeolus luctuosus is in their lengths. The eggs are longer (1.63– 1.75 mm; N = 3) than the mature oocytes (1.08–1.30 mm; N = 7). This presumably results from the female depressing the egg as she attaches it to the cell lining, thereby making the egg dorsoventrally thinner and more elongate and wider than the mature oocyte.