# Immature Stages and Breeding Behaviour of the Hollyhock Weevil–Rhopalapion longirostre (Olivier 1807) (Coleoptera, Brentidae, Apioninae)

## TL;DR

This paper describes the immature stages and breeding behavior of the hollyhock weevil, Rhopalapion longirostre, and its ecological interactions.

## Contribution

The first comprehensive description of preimaginal stages and new insights into the species' reproductive behavior and niche competition.

## Key findings

- Two morphological forms of pupae were identified based on body size measurements.
- The weevil's range expansion is linked to climate change and global warming.
- Competition with Pexicopia malvella in hollyhock fruit limits R. longirostre populations.

## Abstract

New observations on the reproductive behaviour of hollyhock weevil–Rhopalapion longirostre (Olivier, 1807) are presented. The morphology of the preimaginal stages of this species is comprehensively described for the first time. The pupal measurements indicate the existence of two morphological forms: a very considerable number of relatively large individuals (body length: 3.00–3.50 mm) and a few very small (1.75, 2.30 mm) individuals. Competition between R. longirostre and the hollyhock seed moth—Pexicopia malvella (Hübner, (1805))—for the development niche is described. New information is given on the distribution of R. longirostre as well as evidence confirming the connection between global warming and its expansion.

Since the 1960s, the range of Rhopalapion longirostre has rapidly expanded from central Asia to almost all of Europe; it has also been introduced to North America. This expansion is an expression of this weevil’s response to climate change. The phenology of Rhopalapion has been comprehensively described. Its feeding and development are associated with plants from the genus Alcea. Even though more than 300 scientific papers have been written on various aspects of R. longirostre, its immatures and certain kinds of behaviours have yet to be described. The aims of this study were (1) to provide new information on the biology of this species, in particular with regard to the morphology of the preimaginal stages, and (2) to present new observations of its reproductive and developmental behaviour. A total of 73 larvae and 67 pupae were collected from 20 hollyhock plants. Of these, 21 mature larvae and 42 pupae (21 male and 21 female) were measured and described morphologically. The descriptions of both larvae and pupae revealed a number of original features, not previously observed on known immatures of Brentidae. The sympatric development of caterpillars of Pexicopia malvella (Hübner, (1805)) in hollyhock fruit was recorded as a pathogenic factor limiting the numbers of R. longirostre.