Glandular Hairs: Pupal Chemical Defense in a Non-Native Ladybird Beetle (Coleoptera: Coccinellidae)

Combined use of two defensive traits in pupae of Scymnus posticalis ladybirds

“…The droplets may chemically prevent ants from preying on the pupae because their presence deterred ant feeding. Several studies have reported repellent effects of coccinellid pupal droplets against ants, including in Epilachna varivesti (Attygalle et al., ), Subcoccinella vigintiquatuorpunctata (Smedley et al., ), Delphastus catalina (Deyrup et al., ) and against a predaceous coccinellid beetle and a cockroach in E. varivesti (Rossini, González, Farmer, Meinwald, & Eisner, ). The chemicals present in pupal droplets are azamacrolides in E. varivestis (Attygalle et al., ), tocopheryl acetates and ployazamacrolides in E. borealis (Attygalle et al., ; Schröder, Farmer, Smedley, Eisner, & Meinwald, ; Schröder, Smedley, Gibbons et al., ; Schröder et al., ), ployazamacrolides in S. vigintiquatuorpunctata (Gronquist & Meinwald, ; Schröder, Farmer, Attygalle et al., ) and tricyclic pyrones and sesquiterpenoids in D. catalinae (Deyrup et al., ).…”

“…A recent study clarified that the spiny structure in the larval stage functions as a defence against predatory ladybirds (Hautier, San Martin, Jansen, Branquart, & Grégoire, ), which would support the hypothesis. Additionally, in some species of Epilachninae, Microweisinae and Scymninae, transparent droplets are secreted from the tips of glandular hairs distributed on their pupal body surfaces (Attygalle, McCormick, Blankespoor, Eisner, & Meinwald, ; Attygalle, Smedley, Eisner, & Meinwald, ; Deyrup et al., ; Lu, Souphanya, & Montgomery, ; Montgomery et al., ; Smedley et al., ). These droplets often contain harmful chemicals such as azamacrolides, polyazamacrolides and sesquiterpenoids (Attygalle et al., , ; Deyrup et al., ; Schröder, Farmer, Attygalle et al., , Schröder, Farmer, Smedley et al., , Schröder, Smedley, Gibbons et al., , Schröder et al., ; Smedley et al., ), which likely act as a defence against enemies.…”

“…Additionally, in some species of Epilachninae, Microweisinae and Scymninae, transparent droplets are secreted from the tips of glandular hairs distributed on their pupal body surfaces (Attygalle, McCormick, Blankespoor, Eisner, & Meinwald, ; Attygalle, Smedley, Eisner, & Meinwald, ; Deyrup et al., ; Lu, Souphanya, & Montgomery, ; Montgomery et al., ; Smedley et al., ). These droplets often contain harmful chemicals such as azamacrolides, polyazamacrolides and sesquiterpenoids (Attygalle et al., , ; Deyrup et al., ; Schröder, Farmer, Attygalle et al., , Schröder, Farmer, Smedley et al., , Schröder, Smedley, Gibbons et al., , Schröder et al., ; Smedley et al., ), which likely act as a defence against enemies. Predatory ladybirds and ants were reportedly observed to back away and clean themselves after touching the droplets (Attygalle et al., ; Deyrup et al., ; Schröder, Smedley, Gibbons et al., ; Smedley et al., ).…”

“…These droplets often contain harmful chemicals such as azamacrolides, polyazamacrolides and sesquiterpenoids (Attygalle et al., , ; Deyrup et al., ; Schröder, Farmer, Attygalle et al., , Schröder, Farmer, Smedley et al., , Schröder, Smedley, Gibbons et al., , Schröder et al., ; Smedley et al., ), which likely act as a defence against enemies. Predatory ladybirds and ants were reportedly observed to back away and clean themselves after touching the droplets (Attygalle et al., ; Deyrup et al., ; Schröder, Smedley, Gibbons et al., ; Smedley et al., ). Furthermore, a characteristic structure known as the “gin trap”, which lies between the abdominal tergites of a pupa, is found to act as jaws in the tribe Coccinellini (Escalona et al., ), suggesting that it contributes to defence (Eisner & Eisner, ).…”

Coccinellids and Semiochemicals

“…The pupal surface of Subcoccinella vigintiquatuorpunctata bears glandular hairs that produce a secretion consisting principally of three polyazamacrolide alkaloids that serve as a potent anti -predator defence; contact with it elicited pronounced cleaning activity by the predatory ant Crematogaster lineolata . Application of the secretion to palatable food items rendered them unacceptable to the ant (Smedley et al 2002 ). species was stronger to trails of C. septempunctata than to those of A. bipunctata.…”