Behavior and exocrine glands in the myrmecophilous beetle Lomechusoides strumosus (Fabricius, 1775) (formerly called Lomechusa strumosa) (Coleoptera: Staphylinidae: Aleocharinae)

Abstract

To become integrated into an ant society, myrmecophilous parasites must overcome both the defenses and the communication system of their hosts. Some aleocharine staphylinid beetles employ chemical and tactile strategies to invade colonies, where they later consume ant brood and participate in parasitic trophallaxis with host ants. By producing compounds that both appease their hosts and stimulate adoption, the beetles are able to live in and deposit their own eggs in the well defended ant nest. In the current paper, previous findings on the myrmecophilous behavior and morphological features of the staphylinid beetle Lomechusoides (formerly Lomechusa) strumosus are reviewed and re-evaluated. Hitherto unpublished results concerning the beetles’ ability to participate in the social food flow of their host ants are reported. Furthermore, we present an analysis and documentation of the behavioral interactions between beetles and host ants during the adoption process, and we report new histological and scanning electron microscopic analyses of the exocrine glands and morphological adaptations that underlie the myrmecophilous behavior of L. strumosus. The main features of L. strumosus are compared with those of the staphilinid myrmecophile Lomechusa (formerly Atemeles) pubicollis. The paper concludes with a description of the life trajectory of L. strumosus and presents a brief history and discussion of the hypotheses concerning the evolution of myrmecophily in L. strumosus and other highly adapted myrmecophilous parasites.

Behavior and exocrine glands in the myrmecophilous beetle Dinarda dentata (Gravenhorst, 1806) (Coleoptera: Staphylinidae: Aleocharinae)

“…Indeed, our observations indicate that Pella only rarely employs strong smelling tergal gland secretions when they are near the host ant colony. Similar results were obtained with Lomechusa and Lomechusoides [8, 9]. Although Pella species are endowed with the appeasement gland complex (see also [11, 12]), they entirely lack the specific adoption glands described in Lomechusa and Lomechusoides .…”

“…Dinarda beetles do not have the so-called adoption glands found in several anterior paratergites of Lomechusa and Lomechusoides [8, 9, 15]. We did not find specific secretory hypodermal cells openings through the cuticle in these regions in D .…”

“…The most obvious abdominal gland structure is the tergal gland between tergites VI and VII. It was first discovered by Jordan [15]in Lomechusa and Lomechusoides , as well as in Dinarda and later confirmed by Pasteels [16], and Hölldobler [8] and Hölldobler et al [9]. It consists of paired clusters of glandular cells with duct cells that open into paired pouches that are formed by invagination of the intersegmental membrane between the 6 th and 7 th tergites.…”

“…The formicaria were constructed out of plaster of Paris casts and included 16 chambers each measuring 4 X 4 cm. Each plaster nest was covered by a glass plate and placed inside a Plexiglas box (26 x 20 cm) as described by Hölldobler et al [9]. In the Plexiglas arena, honey-sucrose water, chopped cockroaches ( Blatta germanica ) and mealworm larvae ( Tenibrio molitor ) were provided as food.…”

“…In order to conceive of possible evolutionary pathways leading to such astounding myrmecophilous adaptations, we have previously investigated other rove beetle species of the genus Pella , that like Lomechusoides and Lomechusa , belong to the subfamily Aleocharinae, but live as scavengers and predators in the peripheral zones around the nest, at the “garbage dumps,” and on the ants’ foraging trunk routes [10]. Some of the behavioral features of Pella seem to closely resemble those of Lomechusa and Lomechusoides , such as employing a chemical appeasement behavior when encountering host ants [9]. This appeasement behavior appears to be an important prerequisite for living closely with ants.…”